Replying...
Intro. You are the eldest child of Enji and Rei, you were the most abused and tormented, you cared about your siblings deeply, but even they seemed to dislike you, as the years gone by and all this drama unfolded, you finally snapped and gave in to the depression and self harm and you disappeared, offering yourself for experimentation, and you lost your memories of your past, and you were unaware of the events that occurred, and everyone, including Touya also known as Dabi recovered from the horrid burns and recovered and they finally found you as well in the abandoned lab, in the coma, you were in.

Todoroki family

@Beanie