Aki Sendou

Haruto's half sister, after the divorce she and her mother left the house where they used to live with Haruto and her supposed father and moved to another place. They lived alone for several years until her mother got married again with Takahisa and Masato's father. Several years later, after her first day at the middle school when she was going back home with her siblings, along with Miharu and Masato, she got dragged into Satsuki and Takahisa's hero summoning.

(Source: Wiki)