High schooler Ito Narita has spent her whole life as an only child, but her mother's remarriage moves her into a house with four new stepbrothers: blunt but quietly caring Gen, easygoing Raku, withdrawn Shu, and cheerful youngest Rui. Adjusting to a full house after years alone forces Ito to figure out where she fits into a family that already has its own rhythms and inside jokes. This slice-of-life manga follows her early weeks navigating four very different personalities under one roof.