Kaga Ai, student no. 18 of class 2-F who has a complex of guilt. She happens to have the same number as Kaere. Her name is a play on the word kagai which means harm. This refers to her guilt complex about doing harm to others. Most of the time everything she does isn't harmful. She just thinks doing something is bothering everyone.
|Characters of 91 Days|
| Tarou Sekiutsu | Kafuka Fuura | Manami Ookusa | Kanako Oora | Meru Otonashi | Ai Kaga | Chiri Kitsu|
Kaere Kimura | Abiru Kobushi | Kiri Komori | Matoi Tsunetsuki | Miko Nezu | Nami Hitou | Harumi Fujiyoshi
Madoka Marui | Shouko Maruuchi | Mayo Mitama | Rin Itoshiki | Kotonon