Eri is the granddaughter of the Shie Hassaikai's boss. She was also the key source of Kai Chisaki's operation to manufacture a Quirk-Destroying Drug. She has been living at the U.A. dormitories since she was rescued. Eri is a small girl with bluish, off-white hair, messy and unkempt, which is parted in the middle of her forehead, almost reaching down to her waist. She has very wide, innocent-looking eyes, which are bright red in color. Poking out from the right side of her forehead is a small, brown horn, which grows larger when her Quirk is activated. In her first appearance, she's wearing a plain, short-sleeved dress, which is a dirty, pale tan color. Bandages are wrapped around both her arms and legs, stopping at her wrists and ankles, underneath which she is shown to have numerous scars. After she's taken in by U.A., Eri's outfit is changed to a white dress shirt with a frilled collar and a plain red pinafore with two large, golden buttons on either side of her chest. Under this, she wears gray tights and a large set of tan boots, and a small dark red messenger bag with the strap sitting over her right shoulder, and a little floral pattern decorating one of its sides. Her hair also looks to be better cared for, appearing straighter and neater than it was during her time with the Shie Hassaikai. Because her mother disowned her after she accidentally made her father disappear with her Quirk and the experiments she was subjected to by Kai Chisaki, Eri became a fearful and secluded girl, without anyone showing affection to her in her life. Apparently, Izuku Midoriya's touch was the first time she ever felt kindness, which overwhelmed Eri and brought tears to her eyes. When murderous intentions are directed towards her, she neither screams nor cries but simply remains silent in knowing that she has no choice but to accept whatever will happen to her. Although Eri's attempts at resisting and escaping her abuse slowly diminished, she still made numerous attempts to escape her captors, despite knowing nobody she could turn to. Eri is, however, willing to let herself go with Kai in order to protect those who help her, as she feels guilt over other people getting hurt in order to rescue her. This is a result of Kai manipulating Eri into believing that her existence and Quirk are only meant to harm others. As such, Eri feels strong and horrible guilt and does not want other people to die because of her. Unfortunately, after her rescue, Eri still psychologically suffered from Kai's influence, as she was unable to smile due to having no experience of being happy. However, this changed, thanks to the events of the U.A. School Festival, where Eri finally smiled for the first time and expressed her joy at Class 1-A's band performance. Following this event, Eri becomes more cheerful around those she is familiar with and slowly accustoms to her new life at U.A.. At first, Eri still felt negative about her Quirk and was apologetic to her carers at U.A. when believing that it was causing them trouble. After Izuku encouraged her that Rewind could also be used for good, however, Eri develops a more positive outlook both in general and in regards to her power. This improvement is later shown when she is able to restore Mirio's Permeation, telling the latter not to be sorry, and that she had been training Rewind to bring his power back as a means of thanking him while tearing up in happiness. Due to her previous upbringing and isolation, Eri is still rather unfamiliar with many regular concepts and day-to-day things. This includes holidays, as she mixed up Halloween, Setsubun and Easter with Christmas.