Kei Tachikawa is the A-class leader of Tachikawa Unit and Ranked #1 attacker.

Tachikawa is an arrogant person. He also likes to tease Miwa. Kei also acts like Jin, they have a similar way of thinking, which makes him unliked by Miwa. Despite that, he's quite friendly outside the battlefield. He likes to joke around, just like Jin.

(Source: World Trigger Wiki)