Izumi Akazawa

Occupation: Middle School Student
Grade: 3rd year, 3rd class

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

Novel: She dies from falling off a veranda and breaking her neck when pursued by the assassin during the summer trip. One of the seven "Deaths of August".
Manga: Doesn't die just cuts her hair short.
Anime: Same as novel but dies from broken glass while trying to kill Misaki, who she thinks is the extra person.