13 Best Tried and True Japanese Women's Warm Innerwear in 2022 (Uniqlo, Gunze, and More)
Brrrrrrrrr! It's freezing! I wish I had a super-warm, comfortable shirt that wasn't bulky to keep me nice and toasty in winter... mybest is here to help!
Our editors searched Japanese e-commerce sites such as Amazon, Rakuten, and Kakaku.com for the best warm innerwear shirts available online. We then picked out the most popular products and tested them.
In our evaluation, we focused on 3 things:
- How well did it generate heat?
- How comfortable was 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 warm inners available online.
Quick List - Top Japanese Women's Warm Innerwear
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How to Choose Japanese Women's Warm Innerwear
We have a few tips to help you choose the best warm innerwear.
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.
② Find a Material That Retains Heat and Has a Nice Texture
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.
③ Go with Something That Looks Good, Even if You Just Cover it Up
Even if you plan to use it only as an undershirt, there may be times when it shows. What if it peeks out from your sleeve during a job interview, and it looks like grandma pajamas?!
Even if you're not so fashion-conscious, a nice design can be worn as a shirt by itself, so it's more versatile. Consider the neckline, sleeves, hems, seams, color and texture.
5 Best Japanese Women's Warm Innerwear Ranking
Products | Image | Click to purchase | Key features | |
|---|---|---|---|---|
1 | Gunze Inner Shirt Hot Magic | | mybest's Top Choice! Comfortable and SO WARM! | |
2 | Itoyokado Seven Premium Lifestyle Body Heater | | Perfectly Warm, Thick, and Inexpensive | |
3 | Uniqlo Heattech Extra Warm | | Recommended for Moderate and Comfortable Warmth | |
4 | Muji Cotton and Wool Warm Midwinter | | Recommended if You Want Natural Fibers to Keep You Toasty | |
5 | Wacoal Amazing Clothing Natural Material Plus Knit Top | | So Thin, You Can Wear it Like a Second Skin |
mybest's Top Choice! Comfortable and SO WARM!
It's as warm as a sweater, without any of the bulkiness! If you wear this indoors, you could just top it with a T-shirt and be perfectly toasty.
The excellent heat generation comes from the fact that it's 20% acrylate fiber, whereas most inners use less than 10%. It's thick and has a fleece texture, but it's very stretchy and doesn't feel tight or stiff at all.
Unfortunately, we gave it low ranks for design. It's really not very fashionable at all. But for roomwear or as an undershirt to keep warm while enjoying outdoor winter activities, it can't be beat.
ItoyokadoSeven Premium Lifestyle Body Heater
Perfectly Warm, Thick, and Inexpensive
This inner is thicker and denser than others. The heavyweight fleece lining which makes it feel warm the second you put it on. Because it's thick fabric, even if you sweat no one will notice.
The somewhat tight neckline means no part of your shoulders or back will be left out in the cold. The ribs and seams are narrow and fine, so there is no looseness.
Although it's clearly meant to be worn as an undershirt, it looks fashionable enough to wear by itself for a comfy evening at home.
Recommended for Moderate and Comfortable Warmth
Although this shirt is warmer than the regular Heattech line, it's not quite as warm as our top two choices. So if you want a gentle heat that isn't overwhelming, it's perfect.
The lining is very soft and comfortable, and the fit blocks cold air securely. Heat retention is very good. If you simply must have a Heattech product, we recommend this one.
Recommended if You Want Natural Fibers to Keep You Toasty
This shirt is really warm- in fact it tied for first place for heat generation. You could get away with wearing it by itself indoors and be just fine.
But as anyone who's worn wool knows, it can get a bit itchy. If you are sensitive to that, this isn't a good choice for you. The natural fabric also tends to attract lint, so we sometimes felt it looked dirty.
But the overall fit is good, and it's super warm, so if you don't want synthetic materials, choose this one.
WacoalAmazing Clothing Natural Material Plus Knit Top
So Thin, You Can Wear it Like a Second Skin
This was not the best ranked for heat production, but it still kept us pretty warm. What we really liked best, though, was how thin and easy to wear it was.
It's 90% cotton, and many of our testers thought it felt great on our skin. You'll be able to wear it all day and night without even feeling it's there. The design is simple, but the hems are sewn carefully, so it could be worn by itself and not just as an undershirt.
How We Tested the Shirts
We put each product through 3 tests. The products were then given grades from 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 both synthetic materials AND natural materials can generate heat well. The highest-performing shirts were one with a 20% acrylate fiber blend, and another with a cotton/wool blend.
Test ② Was it Comfortable?
Our testers wore the shirts and rated them for how they felt and whether or not they were warm. We looked for fabrics that were not stiff or itchy. We also gave lower rating to ones that were too thin or felt cool to the touch. Our results showed that brushed, fleecy inners were the warmest and most comfortable.
This type of material feels warm as soon as you put it on. It's soft, too. We didn't notice a consistent difference in comfort between natural and synthetic fabrics; some of the natural materials felt itchy, and some of the synthetics were uncomfortable.
Test ③ Was it a Good Design?
We checked the size and cut of the collar, the sleeve length, and the color and texture of the fabric. We also looked at how the seams were sewn. The highest scores went to products that look nice enough to wear as outer shirts, or showing partially under another shirt like an unbuttoned flannel.
We gave low marks to shirts that were so thin they were see-through. We also were unimpressed with necklines that left our bra straps exposed. Heavier weight fabrics and deep V-necks scored better.
Here Are Some More Tips to Stay Warm This Winter!
To keep your body warm from the inside, try to:
- Eat foods that are warm. Root vegetables like ginger, carrots, and onions, and spicy vegetables such as leeks, garlic and chilis are known for their ability to raise the body's temperature. Of course, hot drinks and soup are great, too.
- Improve your circulation and raise metabolism. Soaking in a hot bath, getting exercise, and avoiding strict diets are good ways to keep your muscles warm.
Looking for More Ways to Survive the Cold Weather? Check Out These Related Links!
You'll need a lot more than good innerwear to stay comfortable during the cold winter months. Here are some other great products to help you survive!
Writing: Sayako Suzuki/Translation: Susan Lucier-Ogawa/Photos: Koichi Miura
Top 5 Japanese Women's Warm Innerwear
No. 1: Gunze｜Inner Shirt Hot Magic
No. 2: Itoyokado｜Seven Premium Lifestyle Body Heater
No. 3: Uniqlo｜Heattech Extra Warm
No. 4: Muji｜Cotton and Wool Warm Midwinter
No. 5: Wacoal｜Amazing Clothing Natural Material Plus Knit Top
View Full RankingThe descriptions of each product are referenced from content available on manufacturer, brand, and e-commerce sites.