Yoshio Akamatsu

Boy #1 Yoshio Akamatsu is the first student to leave the school where they are briefed in all versions of the series. The novel describes Yoshio, the largest student in Class 3-B, as "the timid type." Prior to the game, many students targeted Yoshio with pranks and insults.

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He runs away, but later comes back and climbs onto the roof of the school, in an attempt to assassinate others. He is the first student to kill someone - Mayumi Tendo. In the novel and manga he shoots her back from behind, killing her. In the film he shoots Mayumi in the neck. He later attempts to kill Shuya Nanahara, but ultimately fails. In the manga Shuya attempts to convince Yoshio to join him, but Yoshio becomes paranoid and attempts to kill Noriko. Shuya knocks Yoshio unconscious; after a period of time Kazushi Niida kills Yoshio. Yoshio Akamatsu is the fourth student to die.

(Source: Wikipedia)