Oneechan ga Kita

His father's remarriage brings Tomoya Mizuhara an older stepsister, Ichika. While Tomoya is still adjusting to the change, Ichika has already decided that her new little brother should be the center of her attention.

Her enthusiasm leaves him struggling for personal space and an ordinary school day. Ichika's friends and Tomoya's classmates add further complications as he navigates embarrassment, unexpected support, and the awkward process of becoming family with someone who has skipped straight to intense devotion.