Since it's something you wear against your skin 24 hours a day, if you're choosing based on "comfort"

Left: WACOAL MEN Hem-Fitting Pants ¥3,780, LL size ¥4,104 Center: SIDO Bandage Pants ¥4,752 Right: SEEK 3,024

Left/With a unique design that prevents the hem, waist, and front from shifting, these boxer briefs offer a comfortable fit even when you're moving. Designed for ultimate comfort, these boxer briefs feature a passionate pattern that's sure to lift your spirits.
You may have experienced discomfort from the hems of your boxer shorts riding up. However, these "hem-tight" shorts, as the name suggests, are designed to prevent the hems from riding up, so you can wear them with peace of mind. They also have a smooth feel thanks to the use of 60-gauge high-gauge nylon.
View Wacoal Men related products at Isetan Online Store

These bandage pants from SIDO are made with "HOHTAI®," a patented fabric developed in-house using medical bandage material as a base. A collaboration with textile designer Toshimi Onozaki, this piece has evolved into a fashionable garment. In addition to excellent breathability and a comfortable fit that makes you forget you're wearing them, the vintage-inspired design with attention to detail is also a major draw.
View related products from Sidoh at the Isetan Online Store.

Right/ SEEK a familiar name in innerwear! The biggest feature is the original design, which uses Gunze's "Cut-Off®" technology, a long-established Japanese underwear manufacturer, to finish the edges of the fabric in a raw, unstitched state. Because there are no seams at the hem and it is flat, it does not show through outer clothing and can be worn neatly with trousers.
This item features a soft, stretchy knit elastic waistband to reduce tightness.
View related products from SEEK at the Isetan Online Store.

Shido Bandage Pants ¥4,752 View Product

Also recommended are the long boxer-style Sidoh bandage pants made with "HOHTAI®" material and without an elastic waistband! The A-line structure conforms to your body for a gentle fit. Because there is no elastic waistband, you won't feel any tightness, and you can experience a comfortable, liberating feeling.

zimmerli Boxer Shorts/Business Class ¥8,532 View Product

"The comfort is exceptional!" says Ohashi, giving his seal of approval to Zimmery, a long-established Swiss underwear brand chosen by executives from around the world. The thin, lightweight fabric has a silky sheen and a smooth feel, and is made from high-quality extra-long staple cotton. Each piece is carefully sewn by veteran craftsmen, resulting in a beautiful item that you'll want to admire. Another key point is that it doesn't easily lose its shape even after being worn for many years.
Related articles
[Interview] The CEO of the long-established Swiss brand ZIMMERIL says, "Successful men wear high-quality underwear."

Tani Boxer Shorts ¥3,024

Featuring a design that prioritizes simplicity and a meltingly smooth texture, these boxer shorts, available from this season at Isetan Shinjuku Store, Men's Building , are so comfortable you'll want to keep touching them. The Micro Modal® fabric used has a silky feel. Micro Modal® is a fiber made from beech wood, and its fine, long fibers allow for the creation of a fabric with a pleasant feel against the skin.