Rei Todoroki/Synopsis

History
At some point in her life, Rei wed Enji Todoroki in a Quirk Marriage, who used his influence as the No. 2 Hero to force her family to agree. She appeared to be unhappy in this union, as her son Shoto would have memories of her crying very often.

When Enji began to ruthlessly train Shoto when he was five, she would attempt to intervene, but was physically assaulted as a result. Despite this, she supported her son and encouraged him to push through the hard times. When Shoto expressed his worry over someday becoming a man like his father, she assured him that he could become whatever he wanted to be, and that he was not bound to his bloodline.

At some point, Rei began to lose her sanity because of Endeavor's abuse, finding it painful to look at Shoto because his left side reminded her of Endeavor. One day, while she was talking with her mother over the phone and discussing that she no longer had the stability to raise her son, she was startled by Shoto's sudden appearance at the door. Seeing his red hair, she snapped and poured boiling water from a nearby kettle over his head, severely burning his face. She immediately snapped back to reality and tearfully apologized, using her Ice Quirk to soothe the wound.

Shoto bore no ill will over this incident, instead directing it at his father, whom he blamed for his mother's suffering. Some time after the incident, Rei was admitted to a psychiatric ward.

U.A. Sports Festival Arc
The day after the U.A. Sports Festival, Shoto visits his mother in the hospital. Rei is staring out the window and turns around when he enters. During Shoto's visit, she apologized through tears to him, and smiled as Shoto told her he bore no ill will against her and knew she did not mean to harm him and he forgave her a long time ago. She then told him that she wanted him to be happy and save people, which allowed Shoto to finally leave his past behind.

Pro Hero Arc
Her children Fuyumi and Natsuo visit Rei in the hospital. Smiling, Rei shows off the letters Shoto has sent her. Natsuo tells her that Endeavor was promoted to No. 1 Hero, and Rei reveals that Enji has visited repeatedly but they have not faced each other.