She was originally one of the summoned heroes but later betrayed her classmates to the demons. Used her original darkness magic "Soul Bind" to manipulate countless numbers of dead puppet soldiers. After she obtain the power of apostle, she became more powerful than before and able to manipulate Kouki Amanogawa using soul bind even without killing him. She died using self destruct power which is 'last loyalty' after knowing that Kouki no longer being manipulated by her. After she died, she has a face to face communication with best friend Suzu Taniguchi, telling her she would have been better if she met Suzu first instead of Kouki during her childhood time.
After the manipulating Kouki to her side, she behaves just like her mother by being clingy towards Kouki.
Eri has short black hair that is kept in a tiny bob. She has brown eyes and is usually seen wearing glasses.
After obtaining the power of an apostle, she grows wings.
In the beginning, Eri is portrayed as a calm and quiet girl that loves books. Later on, however, it is shown that she is very cunning and willing to take advantage of classmates for her gain. She has a very deep obsession on Kouki to the point that she is willing to kill him to 'soul bind' him and make him her puppet.
She pretended to be friends with her classmates but truth, she doesn't care about them as they are nothing but pawns to her. She attempted to kill her classmates to become her zombie slaves. However, she is also a coward who terrified of her now monstrous and murderous classmate, Hajime Nagumo and begged him to spare her life to bring Kaori back as his slave but failed to kill him after witnessed his wrath of destroying her zombie slaves. She is shown to be even more terrified when Hajime fed Hiyama to the monsters.
She has a knowledge of Daisuke Hiyama's previously betrayal. She used this knowledge to blackmail Hiyama to cooperate with her to ensure they will get those who they've obsessed until failed due to Hajime's arrival.
In her tragic of her past, she was blamed and abused by her mother after her father died by a car accident. After her mother's remarriage, she was abused by her stepfather until his sentence to prison by the police. After her stepfather jailed, her mother abused her even further until the police arrested her as well. She holds a hatred toward her mother for her remarriage and broken her bond between herself and her mother.
- Countless Templar Knights
- Reichi Kondou (alive)
- Herself (explosion)
Following her defeat by her former best friend, Suzu, Eri committed suicide to explode herself and attempted to kill anyone to get closer to her but failed.
- Eri was one of the four (formerly five) classmates who died (along with Yukitoshi Shimizu, Kaori Shirasaki (formerly due to her revival), Reichi Kondou and Daisuke Hiyama). She is the only one who committed suicide by exploded herself.
- Her death suicidal by exploding herself for her attempt to kill Suzu similar to Deidara.
- She was the fourth (formerly fifth) and final classmate to die.
- She was one of the few who had tragic lives (other beings are Hajime Nagumo and Yukitoshi Shimizu).
- She was one of the three who killed their own classmates.