Izumi Akazawa

She holds a grudge against Mei and Kouichi for ignoring the rules, which makes the countermeasures useless, causing the deaths to continue.

In the novel, she dies from falling off a veranda and breaking her neck when pursued by the assassin during the summer trip. Her death is one of the seven “Deaths of August.”

In the manga, she does not die and just cuts her hair short.

In the anime, she dies from broken glass while trying to kill Misaki, who she thinks is the extra person.