|Japanese VA||Satou Azusa|
|English VA||Kendall McCellan|
While in high school, she is a plain, yet beautiful girl with middle-long black hair that is kept in a ponytail. At the front, her hair is parted in the middle, with some strands falling besides her face. She wears ordinary glasses. Her clothes consists of the school's uniform: a dark blue blazer, white shirt, a short skirt, and a tie.
- Nobutaka Oda: She had with him.
Aiko only appeared in the story in Sakamoto's flashback in high school. There, she was the object of Sakamoto's affection. Even though he was in love with her, he didn't have the courage to confess to her. After Sakamoto told Oda about his feelings for Aiko, Oda insulted him being too naive and being an idiot. Oda explains that if Sakamoto is too passive, Aiko would be with someone else. The next day of class Oda had sex with Aiko after she has confessed to Oda. When her friends and Oda's girlfriend found out about it, she burst into tears in guilt and Sakamoto attacked Oda, partially because of Aiko.
- ↑ Btooom! manga, chapter 42, page 31