The body of the shirt uses a classic shirt material: a high-quality, high-density twill fabric woven from 120/2 extra-long staple cotton and silk. The dyeing process begins with using Indian indigo, which boasts a very high purity and a long tradition and history, as the raw material. Skilled artisans meticulously repeat the dyeing and washing process multiple times to create a deep, ultra-deep indigo blue. By combining this with the deep-colored mud dyeing techniques used in the Kyushu region, which are rich in iron, created a "mud indigo dye" that is very tasteful and has great depth. This is an extremely elaborate natural dyeing process, meticulously carried out by skilled artisans who repeatedly dye and wash the fabric over time.