One of the first things that struck many Japanese about サッカー日本代表 (sakkā Nippon daihyō, Japan's national soccer team), at the World Cup in Russia was the uniform.
The shirts of the 代表ユニフォーム (daihyō yunifōmu, national team kit) had traditionally been blue (hence the nickname Samurai Blue), but this year it was a darker shade of 藍色 (ai'iro, indigo). Adidas named this color 勝色 (kachi'iro, victory color), repurposing the name of an off-black color worn by the 武士 (bushi, warriors) of 戦国時代 (Sengoku Jidai, Warring States Period) Japan. Kachi'iro garments are worn under the 鎧 (yoroi, armor), and "kachi" has the double meaning of 勝つ (katsu, winning) and 喝を入れる (katsu o ireru, fusing the body with energy).
The shirt's V neckline with its streak of red represented the kimono as well as the 日の丸 (Hinomaru, Japanese flag). Another salient feature of the shirt were the vertical 刺し子 (sashiko, stiches) on the front, which many Japanese associated with the 千人針 (senninbari). The senninbari, or "stitches of 1,000 people," were belts carried by soldiers during World War II that were meant to ward off disaster and ensure the soldiers' safe return. The senninbari went out of style with the end of Japanese militarism, but sashiko stitching has remained in traditional Japanese textiles and garments. That they showed up on the daihyō uniform at the 2018 World Cup is notable, since the rhetoric surrounding the Japan team has been openly nationalistic ever since manager Vahid Halilhodzic was ousted in April and replaced by Akira Nishino.