All-weather Alpha Jacket


¥ 75,000 Tax included


All-weather Active Insulation for Winter

When hiking in snow, you need to be mindful of your layering. If you layer too much, you get too hot on the climbs. Layer too lightly, and you face getting cold during your breaks.

Down jackets provide too much insulation when moving and are way too hot on trains or in heated mountain huts, etc. With active insulation gear, you don’t need to worry about taking layers on and off because of its high insulation and breathability. However, until now, we haven’t seen a jacket that could cope with the fierce winds and blizzards of winter hiking.

Our new All-weather Alpha Jacket, combines Polartec Alpha Direct, which excels in breathability and insulation, with Pertex Shield Air, known for its outstanding breathability, waterproofing, and lightweight properties. This jacket is comfortable both while on the move or when resting indoors, and can withstand winter storms and blizzards. A true all-weather active insulation layer made for winter.

Wearing this, you won’t have to worry about layering during your winter hikes anymore.

All-weather Alpha Jacket Features

– Outer shell, Pertex Shield Air that can withstand blizzards and snow.
– High-insulating Polartec Alpha Direct lining (136g/m²).
– Comfortable during activity and indoors compared to down jackets.
– Helmet-compatible hood.
– High water repellency (C6 DWR).
– Quickly ventilate with pit zips.
– Breathable and insulating all in a single jacket.


Glacier White


Made in Akita, Japan

Facing: Pertex Shield Air (100% Nylon) 58g/㎡
Lining: Polartec Alpha Direct (100% Polyester) 136g/㎡
Contrast Fabric: Pertex Shield (100% Nylon) 126g/m²
YKK #3 VISLON®︎ Aquaguard®︎ / Two-Way Open
YKK #3 Coil Aquaguard®︎
505g (Size S)
523g (Size M)
567g (Size L)
610g (Size XL)
UNISEX | S / M / L / XL

Product Story

What is Active Insulation?

Akira Natsume, Yamatomichi Founder

I believe our new All-weather Alpha Jacket is probably the ultimate winter outdoor jacket. It truly mitigates all the stress you may have encountered in winter hiking before. I’d like to share my thoughts on why this is.

Up until now, I have been recommending the Alpha Anorak and the Winter Hike Pants for winter activities. The Alpha Anorak excels in breathability and insulation, making it outstanding for winter hikes. However, it lacks wind and water resistance. An additional outer jacket is necessary when facing blizzards and snow on winter ridgelines. On the other hand, the Winter Hike Pants can be worn in situations where you may get sweaty, in a blizzard, on a snowy mountain and even in your sleeping bag. There is no need to change your clothes or add extra layers on top, (However, depending on the temperature, I sometimes use thermal tights). I appreciated the feeling of being able to go anywhere with just one piece of clothing.

This is what I aimed for with the All-weather Alpha Jacket. To offer the same freedom, as the Winter Hike Pants, to go anywhere comfortably, all with just one versatile piece of gear.

Prototype testing in Yatsugatake, April, 2024

I have used a prototype for three seasons and have really been enjoying it. What particularly stands out to me is the newfound enjoyment of walking through deep snow. The exceptional breathability of the jacket prevents overheating, providing outstanding comfort. Additionally, during breaks, it keeps me warm, and the windproof and waterproof features offer a unique sense of security.

It truly makes walking through fluffy snow walls and building steps a more savoring experience. The ability to find joy in these activities allowed me to concentrate on my actions with confidence. When reaching the ridge after a hike, no matter how strong the winds, I feel secure in the All-weather Alpha Jacket. While I have always found joy in snow hikes, the All-weather Alpha Jacket deepened my appreciation for challenging weather conditions. I once again realized the beauty of tools through this amazing jacket.

The All-weather Alpha Jacket uses the same Alpha Direct on the inside as the Alpha Anorak, and the outer shell features Pertex Shield Air, the same material used in our UL All-weather series. By layering our UL All-weather products over the Alpha Anorak, you can essentially achieve the same level of functionality. However, the All-weather Alpha Jacket is equipped with large pit zips on the sides preventing you from overheating. During a field test, in a rather warmer snow hike (around 15°C), I just opened up and let out some of the heat and could continue hiking without taking it off.

Of course, whether you overheat or not depends on differences in activity level and the individual, so I can’t promise the same for everyone. However, this jacket is reliable even in harsh winter conditions. The development took about four years, the concept and idea formed within the first two and the subsequent two years spent on fine-tuning. The hood and cuffs of the sleeves were particularly long. We spent time refining the direction of each shape, creating over a dozen prototypes to ensure ease of movement, and sufficient functionality.

When facing design challenges, I sought inspiration from masterpieces by major manufacturers. Continuously making numerous prototypes over an extended period. It made me wonder how much time was invested in refining them through our own piece. The process of making and refining prototypes over and over is a journey, and through that journey, we relearn what hiking gear really is. What an outer shell for winter hiking really is.

As for the All-weather Alpha Jacket, there is one concern, it comes at a high price. However, if you want to enjoy your next winter hike with the maximum comfort that any jacket not matched in today’s market, I sincerely hope you consider getting one.

December 2023

Read More

Product Voice

More fun than ever

Akira Natsume, Yamatomichi Founder Hidenori Maehara, Yamatomichi Kamakura Manager Hirotomo Hirono, Yamatomichi Patterner

A video discussion on our new All-weather Alpha Jacket, by our founder Natsume, Manager of Yamatomichi Kamakura, Hidenori Maehara, and patterner Hirotomo Hirono. They talk about how the jacket can make your next winter hike even more enjoyable when diving into pristine snow-covered mountains.

Form and Function

Windproof and Snow Resistance Active Insulation

Active insulation has been revolutionary for its high breathability. However, separate layering with an additional outer shell has been the norm to keep wind and water out.

The All-weather Alpha Jacket is a groundbreaking piece of equipment that combines active insulation and an outer shell in one. It features the exceptionally breathable and waterproof Pertex Shield Air with a Polartec Alpha Direct lining, known for its high insulation and breathability. This combination ensures warmth, prevents overheating, protects against high winds, and keeps you dry in deep snow.

In severe winter conditions, the comfort this jacket brings allows you to focus on your activities without the need for intricate layering.

*Note: Since the jacket is not seam sealed, water will seep through in rainy conditions.

Excellent Air-permeability

To ensure high insulation and breathability without hindering the functionality of the Polartec Alpha Direct lining, we used Pertex Shield Air, a breathable waterproof fabric with a nanofiber structure for the outer shell. Compared to layering an active insulation with traditional winter hard shells, this combination brings overwhelming comfort to the user with its high breathability.

We tested the breathability of the hydrophobic non-porous Pertex Shield, a common waterproof breathable material, and Pertex Shield Air.

The test fabric is placed in the middle of the tester. The upper half of the tester has some water in it, while the lower half is empty (filled with air). When the lower half is pressurized by the pump, the fabric lets the air pass, and bubbles are created in the upper half. The more air that passes through, the more bubbles are created. The Pertex Shield with no air-permeability does not generate air bubbles. On the other hand, the Shield Air creates many air bubbles, indicating its high air-permeability.


Compared to down jackets designed for harsh winter conditions, the insulation of this jacket may not be as high, but with the effects of the outer fabric blocking wind allows you to feel warm beyond the numerical value. Add a mid-layer like our Alpha Vest for extra warmth.

Typical outer shells made of breathable waterproof materials lack ventilation, posing a problem when worn during sleep as body heat has difficulty transmitting to the sleeping bag. However, Pertex Shield Air, with its breathability, transfers heat effectively. Being able to wear your main shell to bed allows for a simpler and lighter gear setup.

Helmet Compatible Hood

The large hood, designed to accommodate a helmet, can cover the face up to the mouth when the front zipper is pulled up. Whether the helmet is worn or not, the fit around the face and head can be quickly adjusted by pulling the cords on the cheeks and back of the head. Additionally, the cords on the cheeks can be easily released by pressing the upper button.

Ventilation zippers

To ensure adaptability across a wide range of temperatures while wearing, large pit zips have been incorporated under the arms to enhance ventilation. The zipper pulls are designed with different shapes for the upper and lower ends, making them easy to distinguish even when wearing thick gloves.

Large Inner Pocket

In the two large mesh inner pockets on the left and right sides, you can store items you want to quickly access, such as gloves or batteries or your phone.

The size S is 17-24 cm

Designed for Comfort

We designed the pattern for maximum comfort. The hood and arms will not interefere during movement, so you can stay focused on your hiking.w

Functional Cuffs

The cuffs are made of durable 100 denier Pertex Shield, featuring a lining that is fast-drying and resistant to water absorption. We went through multiple prototypes to ensure the cuffs and Velcro adjusters are user-friendly. Seal the cuffs with an inner glove on and layer over shell gloves to shut out the snow.


The side pocket zippers and pit zips are different colors, making it easy to distinguish the two.

Pull the drawcords at the hemlines to prevent cold air from entering. Quickly loosen by pressing the button at the base.

Inside the side pockets, we utilized a highly breathable lightweight material. This design stops cold air while simultaneously being breathable.

We used a durable 100 denier Pertex Shield for the cuffs and hem, preventing damage from friction and ensuring high durability.


Pertex Shield Air

The Pertex Shield Air is a novel fabric developed by Pertex to further improve water pressure resistance, washing resistance, and overall quality from existing nanofiber membranes.

Nanofiber membranes are net-like structures made of extremely fine polyurethane (PU) fibers that are water repellent (hydrophobic). They have a sponge-like structure with many micropores, allowing the air and moisture to pass through. This air-permeability creates exceptional comfort within the clothes.

The Pertex Shield Air is much lighter than conventional nanofiber fabrics, with a weight of 50g/㎡ to 60g/㎡. For breathability and durability, our proprietary version of Shield Air has 15 denier nylon fabric (40 denier ripstop) as the outer layer and 7 denier nylon as the inner layer. This combination makes it much lighter and more breathable than other nanofiber-based, waterproof moisture-permeable fabrics.

Pertex Shield Air

Pertex Shield Air (100% Nylon) 58g/㎡
Facing: 15d/5f+40d/34f, ripstop
Lining: 7d tricot
C6 DWR (Durable Water Repellent)


Tear strength measured by JIS L 1096 D (In-house test)
Vertical: 4kg, Horizontal: 3kg

Tensile strength measured by JIS L 1096 A (In-house test)
Vertical: 42kg, Horizontal: 31kg

Air-permeability measured by JIS 1096 A (Catalog spec)

Moisture-permeability measured by JIS L 1099 A-1 (Catalog spec)

Moisture-permeability measured by JIS L 1099 B-1 (Catalog spec)

Water pressure resistance measured by JIS L 1092 B (Catalog spec)
10000mm or more

Polartec Alpha Direct

It is like a fleece with longer puffy hairs.

  • Excellent air-permeability and thermal performance
  • Outstanding lightness and packability
  • Polygiene treatment for semi-permanent antibacterial and odor-control

Conventional natural down and synthetic insulators tend to contain body moisture within the clothes and as a result, can be quite stuffy. Polartec Alpha Direct, on the other hand, is so air-permeable that it can be worn even during a high level of physical activity.

Additionally, the material itself is treated with Polygiene, which safely inhibits the growth of microorganisms and bacteria by incorporating low concentrations of silver ions. As a result, it possesses antimicrobial and odor-resistant capabilities that far exceed the lifespan of regular clothing.

Polartec Alpha Direct (100% Polyester) 136g/㎡

Bursting strength measured by JIS L1096A (In-house test)

Heat retention measured by JIS L1096A (In-house test)

Heat retention measured by ASTM F1868 (Catalog spec)
Min: 0.80CLO, Max: 1.60CLO


  • Hide 178cm-75kg
    Size L (Mustard)

    • Hide 178cm-75kg
      Size L (Mustard)

      • Shiori 167cm-55kg
        Size M (Olive)

        • Shiori 167cm-55kg
          Size M (Olive)

          • Ichiro 170cm-56kg
            Size S (Olive)

          • Ichiro 170cm-56kg
            Size M (Glacier White)

          • Ippei 172cm-62kg
            Size M (Mustard)

          • Ippei 172cm-62kg
            Size L (Black)

          • Pony 173cm-76kg
            Size L (Olive)

          • Pony 173cm-76kg
            Size XL (Mustard)

          • Tsuka 183cm-65kg
            Size L (Black)

          • Tsuka 183cm-65kg
            Size XL (Mustard)

            • Ichiro 170cm-56kg
              Size S (Olive)

            • Ichiro 170cm-56kg
              Size M (Glacier White)

            • Ippei 172cm-62kg
              Size M (Mustard)

            • Ippei 172cm-62kg
              Size L (Black)

            • Pony 173cm-76kg
              Size L (Olive)

            • Pony 173cm-76kg
              Size XL (Mustard)

            • Tsuka 183cm-65kg
              Size L (Black)

            • Tsuka 183cm-65kg
              Size XL (Mustard)

              • Nana 151cm-47kg
                Size S (Black)

              • Kanade 161cm-56kg
                Size S (Mustard)

              • Shiori 167cm-55kg
                Size S (Black)

              • Shiori 167cm-55kg
                Size M (Glacier White)

              • Yumiko 170cm-59kg
                Size M (Olive)

                • Nana 151cm-47kg
                  Size S (Black)

                • Kanade 161cm-56kg
                  Size S (Mustard)

                • Shiori 167cm-55kg
                  Size S (Black)

                • Shiori 167cm-55kg
                  Size M (Glacier White)

                • Yumiko 170cm-59kg
                  Size M (Olive)

                  推奨サイズ / Recommended Size

                  Size S M L XL
                  51~61 59~69 67~78 76~85
                  80~88 84~95 92~102 100~110

                  製品サイズ / Product Size

                  Size S M L XL
                  着丈/Length 76 78 82 85
                  身巾/Body Width 60.5 63 67 72
                  裾巾/Hem Width 54.5 57 61 66
                  裄丈/Neck to Sleeve 86 89 92 95
                  袖口巾/Sleeve Opening 14.5 15 15.5 16
                  • There may be slight variations between actual measurements and the dimensions stated due to factors such as fabric stretch, sewing discrepancies, and other manufacturing tolerances.
                  • Due to wearing and washing, fabric shrinkage may occur, leading to changes in dimensions over time.


                  Low Sustainability of Water Repellency.

                  The durability of water repellency is said to increase with thicker fabric, allowing for more penetration of water repellent agents. However, the Pertex Shield Air UL All-weather series, chosen for the outer shell, prioritizes lightweight and breathability. To achieve this, a thin and highly breathable outer fabric is adopted. As a result, while the water repellency is sufficient at the time of shipment, the sustainability of water repellency is lower compared to thicker materials.

                  While the water repellent is effective, moisture on the fabric surface turns into water droplets and falls off. As it weakens, it may cover the fabric surface like a water film, compromising breathability and leading to potential issues such as condensation build up inside the jacket.

                  If you feel a decrease in water repellency, you can revive it by applying heat, such as using a dryer after washing. If the water repellency doesn’t recover, consider using commercially available water repellent agents for maintenance.

                  Please Note

                  • This product adopts an extremely thin waterproof and breathable fabric for the outer shell. Please be cautious about potential damages, tears, or abrasions from rocks or snagging on trees.
                  • To maximize the waterproof and breathable performance, care is necessary after wearing. Performance may be compromised by the accumulation of dirt, sweat, oils, etc. Wash the product regularly following the care instructions.
                  • If the water repellency is compromised, the breathability may also be lost. If you notice a decrease in water repellency, revive it by applying heat, such as using a hair dryer after washing. However, repeated washing can lead to the loss of initial water repellent agents, and even with added heat, the water repellency may not fully recover. In such cases, use commercially available water repellent agents for regular maintenance.
                  • Due to the lightweight and thin porous nature of the fabric, products containing substances such as petroleum jelly, insect repellents, or ethanol (hair cream, cosmetics, sunscreen, insect repellent, etc.) may cause stains or reduce breathability if they come into contact with the fabric. For removal methods, please refer to the our Journal; #2 – Removing stains from rainwear.


                  Care Instructions

                  Water trapped between the outer and lining fabric can be difficult to drain. Using a washing machine may cause the membrane to delaminate. To keep the product in good condition, always wash and rinse by hand. If you wish to drain the water using a washing machine, put on a short spin cycle of 1 minute or less with the product turned inside out.

                  • Washing machines should be used for spin drying only, and washing should be done by hand.
                  • Wash by hand with a moderate amount of mild detergent in lukewarm water at a water temperature of around 30°C (86°F).
                  • Do not use fabric softener or bleach.
                  • Use a sponge soaked in warm water with detergent when stains are noticeable.
                  • Rinse thoroughly to avoid residual detergent, which may cause discoloration and damage the water repellency.
                  • When using a washing machine to spin, turn the jacket inside out and spin for 1 minute or less.
                  • Do not use a dryer as it will accelerate the deterioration of the adhesive.
                  • Hang dry in the shade.
                  • Periodically apply heat with a hair dryer to restore the water repellency of the outer fabric.
                  • Do not dry clean.
                  • Products containing Vaseline, insect repellent ingredients, or ethanol (hair cream, cosmetics, sunscreen, insect repellent, etc.) may stain the outer fabric and reduce its moisture permeability.


                  • We only accept payment by credit card. We currently do not accept payment via bank transfer from overseas accounts.
                  • We accept the following Credit Cards: Visa, Master, American Express, and JCB.
                  • To download your receipt, please click the link included in the Dispatch Notice, which we will send by email as soon as the items are dispatched.


                  • Order Confirmation will be sent after the order.
                  • The items will be dispatched within 3 days after the payment is confirmed.
                  • The dispatch notice will be sent by email as soon as the items are dispatched.
                  • The delivery may be delayed by unforeseeable reasons such as natural disasters and other logistics issues. We appreciate your patience and understanding.
                  • We cannot ship multiple orders in one package due to how our delivery system is currently set up.
                  • We will ship to regions in North America, Oceania, and Europe (excluding Russia) via DHL. For regions in Asia, the Middle East, Central and South America, Africa, and Russia, we use EMS (International Express Mail Service) for shipping.
                  • Shipping fees and delivery times vary depending on the shipping destination as well as the size and weight of the items.

                  Size Exchange

                  • Overseas customers who need to change the size of their order, should note that the time needed for shipping will vary greatly depending on your country of residence.
                  • We only accept exchanges when the item is unused (except for fitting).
                  • If you wish to exchange the size of the item, please contact us within seven days of receiving your order.
                  • Exchanges can only be made for the same color in a different size.
                  • If the size you wish is out of stock, we will suggest a different color.
                  • If the product is out of stock, we may simply have to ship the item back to you.
                  • All shipping costs to be carried by the customer.
                  • We will only send the exchanged item to you, upon receipt of return shipping cost via PayPal.
                  • Please be aware that some countries charge customs duties depending on the price of the item.
                  • We are unable to answer any questions on local customs. Please contact your local customs bureau.


                  We accept repairs for all of our Yamatomichi products. For inquiries on repair services including patching the holes, repairing with extra components, or fixing the items damaged over time, please feel free to contact us from the “Repair” section of the SUPPORT page.