Toshimasa Kawasaki joins Team Tonegawa as one of its original black suit members. This group, formed under Teiai Group executive Yukio Tonegawa, develops a "death game" project. Kawasaki, aged 30 during this assignment, contributes to the project's planning and operational tasks. He becomes the first team member to contract the flu, temporarily disrupting operations. Outside work, Kawasaki shares a bowling hobby with the other initial black suits. Following the Team Tonegawa events, he resigns from the Teiai Group and transitions to a career at a major bank.