After his father remarries, Yuuta Asamura ends up living under the same roof with a brand-new stepsister, who happens to be the hottest girl in his grade! However, Yuuta and his new sister, Saki Ayase, have no illusions—they both carry trauma from their parents' difficult divorces, and they agree to keep a respectful distance. As it turns out, though, the two have a lot in common, and slowly, cautiously, they grow closer. But is the emotion blooming between them simple admiration, familial love, or something more?