Breathable and Stuffiness-Free Even on Rainy Days—Wear Them Like Dress Shoes! The Power of High-Performance Knit Shoes "ACTHREAD"

In recent years, business attire has become increasingly casual, and pairing sneakers with suits or set-up outfits has established itself as a standard style. However, depending on the workplace or business meeting, many still feel that sneakers are a bit too casual. On the other hand, traditional dress shoes come with their own set of drawbacks: stuffiness, weight, stiffness, and difficulty handling rainy weather. Created to solve these conflicting needs is the high-performance knit shoe line "ACTHREAD."

We spoke with Satoshi Yamaguchi, a merchandiser at Z&K Trading Co., Ltd. who was involved in the development, about how the knit fabric achieves both water repellency and breathability, the engineering required to make it work as a shoe, and the new models "RIPPLE" and "SYMBOL."

Solving the Drawbacks of Dress Shoes with Knit Material

"Solving common daily frustrations with dress shoes through the power of materials"—that was the idea behind ACTHREAD, which features a water-repellent knit upper.

"ACTHREAD launched with the concept of 'changing the business scene from the ground up.' Dress shoes worn in business settings carry everyday stresses like stuffiness, weight, stiffness, and the constant worry of getting them wet on rainy days. Our starting point was finding a way to solve those exact issues through advanced material technology."

The team aimed for a pair that combines the formality of dress shoes with the comfort of sneakers. If the goal was simply to match the appearance of leather, synthetic leather would have been an easy option. Instead, ACTHREAD chose knit fabric for its softness, lightness, and outstanding breathability.

Generally, knit fabric features open spaces that allow air to pass through easily, and its flexibility lets it adapt smoothly to foot movements. On the downside, water penetrates it easily, and it struggles to retain its shape. Furthermore, the soft look unique to knit textures can appear overly casual depending on how the shoe is constructed.

How could they maintain the natural benefits of knit while delivering the water repellency needed for rainy weather and a refined silhouette suitable for professional business styles? Development began right at the level of yarn selection and knit structure design.

Repelling Water While Allowing Air to Flow: The "Yarn" and "Knit" Creating Conflicting Features

"For example, making the fabric thicker increases water repellency, but compromises breathability. We aimed for shoes that guarantee reliable water repellency during the rainy season while remaining comfortable and stuffiness-free even in the heat of summer."

To achieve this, they adopted a method of applying a water-repellent treatment directly to the yarn before knitting it. Unlike post-treatments where a waterproofing agent is sprayed onto the finished surface, the yarn itself repels water and dirt, allowing water droplets to bead on the surface due to surface tension. At the same time, open pathways between the threads allow air to pass through freely.

However, simply using water-repellent yarn wasn't enough on its own to solve the problem.

"If the weave is too loose, water sneaks in; if it's too tight, breathability is lost and the fabric becomes stiff. We experimented endlessly with different yarn counts (thicknesses) and knit structures to strike the perfect balance while keeping the distinct texture of knit material."

The resulting knit material was proven to prevent water penetration even when submerged in 4 cm of water for 4 hours. Furthermore, in an independent spray test under JIS L 1092, it achieved a water repellency rating of Grade 4—the second-highest rating on a 5-point scale. It maintained this level of water repellency even after washing, showing a 0% dimensional change rate in both length and width.

Engineered from a Single Piece of Knit: Balancing Rigidity and Stretch

When adapting knit fabric for footwear, maintaining shape stability is just as challenging as waterproofing. Softness and elasticity are knit's greatest advantages, but if the entire upper stretches freely, the foot shifts inside the shoe during walking, causing the refined silhouette to collapse.

"To solve this, we blended in 'hot-melt yarn,' which fuses when heat is applied to add firmness and structure to the knit. We kept elasticity around the collar where stretch is needed to slip the shoe on easily, while minimizing stretch across the instep. By switching yarn types and knit patterns across different zones, we engineered distinct levels of firmness and stretch within a single piece of knit upper."

Attaching components other than the upper also posed challenges unique to water-repellent materials. Areas prone to wear, such as the toe, require TPU (thermoplastic polyurethane) parts for extra durability. However, materials designed to repel water and dirt are inherently difficult for adhesives to bond with.

"While the high-wear toe area needs protection with a different material, water-repellent knit is notoriously hard to adhere. We tried numerous adhesives and bonding techniques before finally achieving a result we were truly satisfied with."

For the insole, the shoes feature an ergonomically designed proprietary "Resilicell Insole." Urethane foam absorbs landing impacts while supporting the arch of the foot.

Beneath the insole, the midsole incorporates a medium-resilience material tuned to prevent sinking too deep. By pairing a soft feel underfoot with the responsiveness needed to support every step, the structure aims to deliver stable, long-lasting comfort even on long walks.

New Designs Reflected in "RIPPLE" and "SYMBOL"

ACTHREAD originally focused on business shoes positioned right between the sharp look of dress shoes and the comfort of sneakers. Response was particularly strong during the summer from users struggling with stuffy dress shoes, leading to many repeat buyers purchasing multiple pairs. It was this growing support that inspired the development of RIPPLE and SYMBOL.

"When launching the brand, we envisioned items bridging the gap between dress shoes and sneakers. However, we also received requests for dedicated sneakers, which led to the release of these two models. Even so, we made sure the design doesn't feel overly casual, keeping them suitable for business settings as well."

RIPPLE is a slip-on model featuring a motif inspired by ripples spreading across water across the instep. In addition to a laceless design, high-stretch knit is positioned specifically over the instep, achieving both a foot-hugging fit and effortless slip-on convenience.

Meanwhile, SYMBOL is a signature model featuring the ACTHREAD logo at the core of its design. It translates military-inspired functional beauty into a modern sneaker, incorporating a quick-lace system for the shoelaces. Simply pulling the cord allows precise adjustment of the tightness, easily wrapping the entire foot in a uniform fit.

In addition to everyday city wear, it features a spikeless sole designed with golf use in mind as well.

To create a refined look that doesn't feel overly casual, the texture of the TPU components proved crucial. While TPU serves functional roles such as reinforcement and shape retention, a surface that is too uniform or overly glossy looks out of place next to a knit upper.

"To prevent the parts from looking cheap, we applied 'keshibo'—a fine embossed grain pattern that mimics leather pores. Even subtle differences in gloss or thickness completely change the appearance, so we made and adjusted countless samples."

Rather than erasing the differences between materials, aligning the grain of their textures allows them to blend naturally into a single shoe. This softens the ruggedness typical of functional footwear, resulting in a look suitable for both work and casual settings.

By applying water-repellent treatment at the yarn stage and optimizing the knit structure, the material repels water while remaining breathable. Combining this with hot-melt yarn and TPU components preserves the soft feel of knit while reinforcing the shape retention and durability essential for shoes. ACTHREAD seamlessly combines the breathability and lightness unique to knit, rain-ready water repellency, and a sophisticated aesthetic that fits right into business settings.