14 Best Tried and True Japanese Men's Warm Innerwear in 2022 (Uniqlo, Gunze, and More)
Do you like to stay active outdoors in spite of the freezing temperatures? Do you prefer to stay inside, but sometimes feel chilly? Or do you need a winter undershirt for wearing to the office? mybest is here to help you choose just what you're looking for!
Our editors searched Japanese e-commerce sites such as Amazon, Rakuten, and Kakaku.com for the best warm innerwear for men available online. We then picked out the most popular products and tested them.
We focused on 3 things:
- How well did it generate heat?
- How easily could we move around in it?
- Was the design good?
We then ranked the products and put what we learned into a buying guide to help you choose the best Japanese men's warm inner shirts available online.
Quick List - Top Japanese Men'S Warm Innerwear
Gunze
mybest's Top Choice! Our Favorite Heat Generating Inner for Men
mybest US' editing team consists of experienced members who have backgrounds in writing, editing, translation, and more. We are dedicated to researching what makes a product or service the best to users in the US in order to create top-quality articles. From skincare, to kitchen appliances, and to DIY supplies, our mission is to find the best ones for you.
How to Choose Japanese Men'S Warm Innerwear
We have 3 tips for you to help you choose the right warm inner for your needs.
① Choose Innerwear That Has Good Hygroscopic Properties
When you sweat, your body cools down. If you sweat in a cold environment, your body could lose heat rapidly. But if you are wearing hygroscopic exothermic fabric, sweating will generate heat and you'll stay warm. And if you move from a warm room to the cold outdoors, a good shirt should keep your body at the same stable temperature.
Natural material like cotton, wool, and silk are highly hygroscopic. Wool is particularly good, but many people don't like the itchiness. So, wool is often blended with cotton for undergarments.
Synthetic fibers are generally less hygroscopic than natural fabrics. To improve their functionality, they are often blended with acrylate fibers, so look for that term on the label.
② Choose a Material That Matches Your Lifestyle
Speaking of fabrics, you shouldn't just choose one that is the top-seller, because your needs may be different. Depending on the material, the functionality, texture, and care requirements will vary. Below, we've summarized the properties of different materials for you.
Natural Fibers
- Cotton
Cotton feels nice on the skin, has good hygroscopic properties, and is durable. It can be machine-washed. But, it wrinkles easily and dries slowly.
- Silk
Silk feels cool in summer and warm in winter! It's pliable and resistant to static electricity. But it doesn't hold up under a lot of friction, and it can't be washed in the washer. It also gets discolored by sunlight and moths love to eat it.
- Wool
Wool has excellent heat retention and elasticity. It doesn't feel tight, but it can shrink when washing and drying (never dry it in the dryer!) It's also thick, and bugs will eat this, too.
Synthetic Fibers
- Polyester
Polyester is durable, elastic, and wrinkle-resistant. It doesn't absorb moisture easily and dries fast. But it's prone to getting dirty and attracting static electricity.
- Rayon
Rayon has great heat retention and elasticity. It's soft and comfortable, but wrinkles easily and is not machine washable.
- Acrylic Fibers
Acrylic fibers are mold-resistant, hold heat well, and are elastic. But they attract static electricity, can change color when exposed to sunlight, and can melt under extreme heat.
③ Choose a Design You Like
You may want to buy a shirt just for use under another shirt, and think design isn't important. But what if you go into a room that's too hot? If your inner is ugly, you'll be embarrassed to unbutton your collar or roll up your sleeves.
When considering the design, check the thickness of the material and the neck and cuff seams. Be careful about items that are see-through, are too glossy or shiny, or have ribbing that looks like underwear. For use under a work shirt, we recommend a neutral beige that matches your skin.
7 Best Japanese Men'S Warm Innerwear Ranking
Products | Image | Click to purchase | Key features | |
|---|---|---|---|---|
1 | Gunze Innershirt Hot Magic Super Stretch | | mybest's Top Choice! Our Favorite Heat Generating Inner for Men | |
2 | Gunze Innershirt YG Heat & Warm Series | | An All-around Great Shirt | |
3 | Uniqlo Heattech Extra Warm | | Our Favorite (and the Warmest) From the Heattech Line | |
4 | Shimamura Fiberheat Warm Inner | | The Best Inner Shirt for a Loose Fit | |
5 | Uniqlo Heattech Ultra Warm Crew Neck Tee | | The Best Inner Shirt for Lounging around | |
6 | Gunze Body Wild Long-Sleeved Shirt V-Neck | | Recommended to Wear as an Outer Shirt | |
7 | ZOZOHEAT ZOZOHEAT Long-Sleeved Crew Neck | | Recommended if You Want a Custom Fit |
mybest's Top Choice! Our Favorite Heat Generating Inner for Men
This shirt is so warm and thick, you'll be sure to keep nice and toasty no matter the weather. The heat generation is also excellent. It's elastic, and the sleeve length is just right.
Some thought it was a bit too heavy as an undershirt, and we tested a purple one, which we didn't like. The score for design might have been higher if we'd tried another color.
But if you're looking for a warm inner shirt for winter sports, or to move around easily while playing with your kids on a snowy day, this is a great choice!
An All-around Great Shirt
It's not quite as good at heat generation as our top choice, but it's a bit more well-rounded, actually. It's hard to find any disadvantages.
The sleeve length is perfect, and won't protrude from your cuffs. The V-line collar is sharp and the hems are flat.
You could wear it as an undershirt, or by itself, and not feel strange either way. It's also very easy to move around in and the warmth is still top-notch.
Our Favorite (and the Warmest) From the Heattech Line
This has the best heat generation of all the Uniqlo shirts we tested this time. Also, the collar is also a bit more shallow, and it's thicker.
All of this contributes to the warm feeling you'll get when wearing it. It fits snugly and is easy to move around in. If you want to buy from Uniqlo, we recommend this one.
The Best Inner Shirt for a Loose Fit
This shirt has very good heat generation and ease of movement. It's lined with a thick brushed fleece material which is very elastic. The sleeves are long, so it's good if you want full coverage or find other shirts are too short for you.
We don't recommend wearing this one under a tight shirt, though. The sleeve openings are large, and the overall fit is loose.
UniqloHeattech Ultra Warm Crew Neck Tee
The Best Inner Shirt for Lounging around
This is the second warmest we tested in the Heattech line. The fabric is very think and slightly heavyweight.
Although it's marketed as innerwear, our opinion is that the thickness and the overall fit make it better suited to lounging around the house in. It's like a lightweight sweatshirt.
Recommended to Wear as an Outer Shirt
We really liked the design of this shirt. The ribs on the cuffs are thick, and the V-neck collar is a crisp, clean line. The sleeves are a relaxed fit, but the snug cuffs prevent them from drooping onto your hands.
The overall fit is tight but elastic, and the sewing is high-quality. You could top it with a casual jacket and go out to dinner in it!
The only drawback is it isn't very good at moisture absorption and heat generation, so if you want active wear you can sweat in, it's not the best choice.
Recommended if You Want a Custom Fit
This shirt is not off-the-rack, but tailor-made to your specifications. If you always have trouble finding your size, this is a great choice for you.
We gave it high scores for ease of movement based on that. However, you'd probably want to use this one as an undershirt, and not by itself, because even though the heat generation is good, it's rather transparent.
How We Tested the Innerwear
We put each product through 3 tests.
- How well did it generate heat?
- Was it easy to move around in?
- Was it a good design?
Then we ranked each shirt on a scale of A to D+.
Test ① How Well Did it Generate Heat?
Heating fabrics work by producing heat from the absorption of moisture. (This exothermic process is called hygroscopic heat generation, if you're interested in the science!) To test this functionality, we enlisted the help of a specialized institution to measure the level of moisture absorption and exothermicity of the fabric of each product.
The fabric was placed in an environment where the humidity increased over time, and then the change in surface temperature was checked every 60 seconds. Fabric that had a larger temperature difference is better at moisture absorption and heat generation.
Our tests showed that despite all the science of synthetic fabrics, natural fibers have stronger heat-generating power. A blend of cotton and wool performed well. (Of course, synthetics have other advantages, so choose based on your needs.)
Test ② Was it Easy to Move Around In?
We wore the inner and moved around to check the overall fit and freedom of movement. We paid special attention to the shoulders and elbows.
We found that the structure and size influenced the freedom of movement most. Products designed to be used as undershirts were fitted to the body but didn't feel tight. On the other hand, they also weren't too loose, so they wouldn't get in the way of your outer shirt.
Test ③ Was it a Good Design?
Last, we checked the design. How was the neckline, sleeve length, thickness and texture? Were the seams large or small? What about the color? We really liked shirts that looked as if they could be worn by themselves and not hidden under another shirt.
Our test proved that fabric can indeed be too thin. Some of the shirts were so transparent we wanted to wear another shirt underneath!
We also found that flat collar ribs and seams which are inconspicuous are important to give a high-fashion feel and move a shirt from the realm of pajamas to daily wear. However, some of the shirts were overdesigned, which limited their versatility.
Looking for More Ways to Enjoy the Winter Season? Check Out These Related Links!
Now that you're all warm and toasty, it's time to get out there and enjoy! Or you could stay in.
Top 5 Japanese Men'S Warm Innerwear
No. 1: Gunze｜Innershirt Hot Magic Super Stretch
No. 2: Gunze｜Innershirt YG Heat & Warm Series
No. 3: Uniqlo｜Heattech Extra Warm
No. 4: Shimamura｜Fiberheat Warm Inner
No. 5: Uniqlo｜Heattech Ultra Warm Crew Neck Tee
View Full RankingThe descriptions of each product are referenced from content available on manufacturer, brand, and e-commerce sites.
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