You Won't Want to Go Back to Any Other T-Shirt! Mizuno's "365 All-in One T-Shirt" Offers Year-Round Comfort

Japan's renowned sports equipment manufacturer Mizuno has consistently released sportswear made from pioneering high-function materials. Surprisingly, however, the material that took center stage in developing their new T-shirt is the naturally derived "Merino wool".

Wool is often associated with fall and winter, but Merino wool is reputedly cool and remarkably comfortable even in summer.

Released in spring 2024 and immediately becoming a huge hit, the "365 All-In One T-Shirt Merino Wool" makes waves. The project manager now shares everything about its surprising performance and how it came to life.

Merino Wool Delivers Outstanding Performance Even in Summer

When it comes to contemporary T-shirts, cotton and polyester are the most common materials.

So why did "365 All-In One T-Shirt Merino Wool" opt for Merino wool?

"Merino wool comes from the Merino breed of sheep, and its fibers are finer and softer than those from other sheep breeds. Mizuno has long appreciated the functionality of Merino wool, which is often used as a base layer for mountain climbing", says Inoguchi.

Merino wool is more than just a material that keeps you warm.

"The fine fibers trap air and enhance 'insulation.' In addition, its 'thermo-regulating' capability helps keep body temperature balanced amid varying weather, while its 'moisture-wicking' property absorbs sweat and its 'breathability' releases moisture as needed to maintain dryness. It even boasts 'odor-resistance.' Merino wool truly is a high-tech material, crafted by nature itself."

In 2023, Mizuno launched an innerwear line combining its proprietary "Breath Thermo", a fabric that absorbs moisture from the body to generate heat, with Merino wool, which became a hot topic.

"In order to unlock Merino wool's performance and meet Mizuno's strict quality standards, it was crucial to choose a highly trusted material.

We partnered with The Woolmark Company, a not-for-profit organization in Australia devoted to Merino wool advocacy, marketing, and R&D.

The Woolmark logo is a mark of trust; only products that clear rigorous requirements—including fiber content, durability, and wash testing via independent testing institutions—can display the label."

This innerwear with Woolmark certification laid the groundwork for the birth of the T-shirt.

"As I mentioned earlier, Merino wool features thermo-regulation, breathability, and odor resistance—functions that are useful well beyond winter. So our next step was to develop a T-shirt that could be worn solo in the summer."

This is how the "365 All-In One T-Shirt Merino Wool" came to be.

When it launched on the Makuake crowdfunding platform in May 2024, it proved a smash hit, selling over 1,700 units.

The main fabric is a unique blend made by Mizuno, combining Merino wool and polyester in a 1:1 ratio, and holds the Merino Perform certification from The Woolmark Company. This special fabric meets the company's high standards for both quality and material balance.

Combining polyester with Merino wool brings even more benefits.

"On its own, Merino wool may leave something to be desired in terms of quick-drying and durability. By blending it with polyester, we enhanced these properties, creating a highly functional material.

This premium fabric has stretch, moisture-wicking and quick-drying ability, breathability, less stuffiness, and odor control—it's truly the ideal material for sportswear. Of course, it also performs exceptionally as everyday casual wear."

People often worry that wool will feel sticky or prickly, but this fabric feels smooth and surprisingly light against the skin. A close look even reveals a mesh texture on the inside.

The outer surface of the fabric is Merino wool (photo left), while the side that touches the skin is a polyester mesh fabric (photo right).

Thanks to our unique two-layer structure, the shirt excels at moisture absorption, diffusion, and quick-drying properties. Even when you sweat, the dry touch is maintained.

The lightweight material offers ample breathability—making this shirt feel perfectly wearable, even in the summer.

Mizuno's Unique Functionality Nurtured Through Sportswear Development

Mizuno's technology has also been integrated to support ease of movement.

"The high-performance Merino wool and polyester material developed independently by Mizuno is inherently stretchable, but we've gone further and implemented Mizuno's original Dynamotion Fit into this T-shirt as well.

This is a design methodology that verifies movement patterns based on 3D computer graphics analysis and anatomy, skillfully employing specific patterns and sewing techniques in pursuit of ease of movement during exercise."

This significantly reduces fabric pulling and a sense of tightness, resulting in remarkable freedom of movement.

Inoguchi himself even uses it as running wear.

Caring for your T-shirt becomes especially important during the hot, sweaty season.

"As for care, the shirt is Woolmark certified for Total Easy Care. You can wash it in a home washing machine, and it's also dryer-safe. Even with repeated washing, its supple texture remains intact."

So what about issues like pilling common with wool products?

"By using special yarns, we’ve addressed problems like pilling and fuzziness. The yarn is crafted by opening up polyester threads electrically, then twisting Merino wool yarn together—a process that produces a fabric highly resistant to pilling and fuzz."

The odor-neutralizing power of Merino wool also proves exceptionally useful for daily use.

"Merino wool fibers keep your skin dry and prevent unpleasant odors caused by sweat and bacteria. That’s a real advantage when you’re hiking or camping and can’t easily do laundry. I never travel or go on business trips without one myself."

Since it's a T-shirt meant to be worn as a single layer, there's special attention to design.

"The minimalist look, with the chest logo omitted, works for all kinds of outfits. The moderately relaxed boxy silhouette reflects the recent trends, making it perfect as a standalone shirt.

The polyester blend adds just the right firmness to the fabric, giving the silhouette a structured look."

The details showcase clever design choices, too.

"The neck is cut slightly higher at the back, enhancing comfort when you throw a jacket over it. Plus, the T-shirt’s sleeve hems are crafted to stay in place and not ride up when slipping on a jacket."

The refined texture, unique to the Merino wool blend, is also a reason it pairs so naturally with a jacket.

The hem is adorned with a woven label featuring both the Mizuno and Woolmark logos.

"It's the world's first Merino wool T-shirt—the 365 All-in-One T-shirt Merino Wool—to be jointly certified with Merino Perform and Total Easy Care Woolmark and commercialized under a unified label (according to Mizuno research, as of 2025)."

The model name "365" represents the versatile utility of this T-shirt.

"In summer, wear it solo; in winter, layer it as an innerwear. It’s good for business, outdoor activities, outings, sports—really, it fits a wide range of scenes. We called it '365' because it can be worn all year round, regardless of the season.

It's popular with all ages and genders, but with unexpectedly high demand for business use, we’re planning to release a polo shirt version next."

Many T-shirts made from standard Merino wool cost over 10,000 yen, but this one is in the 6,000 yen range—making it a great value.

"We worked hard to keep the price accessible so that it could be used as daily wear by as many people as possible."

This hybrid T-shirt, combining all-natural Merino wool with polyester, is thoughtfully engineered for maximum comfort and practicality.

It sets a new standard for what an urban lifestyle T-shirt can be.