Otouto no Kyorikan ga Baguttemasu

Hana Yoshida, a high school freshman, falls in love with her classmate Taisei Hagita. But when their parents remarry, Hana and Taisei become sisters and brothers. Hana puts her feelings away and vows to become a good family. But when Taisei starts living in the same house with Hana, she feels too close to him, and every day is filled with excitement...?