Eri

Eri(壊理) is a young girl that Chisaki claims to be the father of.

Appearance
She is a child with bandages all over her body. She has a small horn on the right side of her forehead and has long, choppy, unkempt hair.

Personality
She is a frightened little girl who doesn't want to take part in Chisaki's plans. Because of this, Chisaki considers her a "troublemaker".

She is however willing to let herself go with Chisaki in order to protect those that help her.

Synopsis
Eri was running down an alley away from Chisaki, mentally chanting she had enough of her treatment and wishing someone would save her. She bumps into Izuku and Chisaki catches up to them.

Quirk and Abilities
Unknown Quirk Negation: Eri's blood is able to attack an individual's Quirk and stop its activation.

This ability within her DNA makes Eri an important part to Chisaki's plans. Supposedly, he is using her blood to stop the activation of Quirks in order to control the people (much like how All For One controlled people by taking away their Quirks) and using that as a means of destroying justice.

Due to the unknown nature and lack of information so far about this ability, much of Eri's abilities remain mysterious. It is unknown if this is her Quirk, another form of mutation or even how this negation ability works. With what little information is gathered, her ability can be distinguished with the following possibilities:
 * 1) So far, the effects of her blood only temporarily stops the activation of a Quirk.
 * 2) Judging from the process and effects of the darts that carry her blood and cells, it can be assumed the Quirk negation can only work if her blood enters the body in anyway.
 * 3) It is explained by Eraserhead that his Quirk's negation is different from Eri's blood. Eraserhead's Quirk is merely negating the activation of a Quirk while Eri's blood attacks the Quirk itself.
 * 4) It is also possible her ability is incomplete. Nighteye suggested the possibility of Chisaki attempting to perfect the blood/drug to completely remove an individual's Quirk.
 * 5) From the information explained in the previous point, it can be also assumed due to the attempts by Chisaki and his organization to perfect the drug, Eri's blood is altered to fulfill the requirement. This leaves the true ability of Eri's blood and its original effects questionable.

Chisaki
Similar to how he treats his members, Chisaki only values Eri for her use. However with certain members, like Chrono, Chisaki values Eri enough not to consider her to be disposable.

Eri is terrified of Chisaki. Her fear of Overhaul is strong enough to make her not disobey him when he gets serious.

Izuku Midoriya
He was the first person she bumped into when running away from Chisaki. She tearfully pleaded for him to not leave her alone with Chisaki and to help her. Izuku was suspicious of Eri's unnatural treatment. Even though he was instructed to remain covert around Chisaki and despite the interventions of Mirio and Chisaki's rebuttals, Izuku desired to protect Eri.

When Chisaki took off his glove and revealed his killer intent, Eri immediately went back to him. Izuku was shocked and confused by her behavior. He wanted to reach out to her but was held back by Mirio. He could only look on in worry as she was taken away.

When Izuku learnt the origin of the Quirk attacking darts and its connection to Eri, he was devastated and felt immense regret for not rescuing her when he had the chance. He felt responsible for Eri's situation and resolved to rescue Eri no matter what.