Ooizumi Shiori

This game’s main heroine. Plays basketball and joins the school team. Despises her older brother that only plays eroge at home, and applies minimal/ignore routines to Ryou. Due to her height, she practices basketball everyday and comes home late, but still cooks for herself and Ryou and do all the housework… until all of the sudden another challenger has appeared.

From Warum's review

After her parents divorce her name changes to Nitta Shiori (新田 栞)