緒山さんの家庭環境は複雑。腹違いだけどどっちもまひろとみはりの子。
誕生日は同じ日だけどお兄ちゃんの方がちょっとだけ早く出てきたからお兄ちゃん。
きっと最終回みたいに手を繋いで二人一緒に頑張ってた。

Oyama-san's family background is complicated. Although they have different mothers, they are both Mahiro and Mihari's children.
Although they have the same birthday, onii-chan was a bit earlier, so he's the onii-chan.
They probably did their best together while holding hands like in the final episode.