[Rocomani (Manatsu Roco)] On That Day Together With My Fiance's Little Sister

What begins as a peaceful domestic life with a warm, welcoming family takes a sudden, intense turn when a spirited younger sister makes her intentions known. Yuuyu, a cheerful yet unpredictable girl, creates a chaotic tension that threatens to disrupt a stable relationship. As her bold and unpredictable nature unfolds, the boundaries between family affection and obsessive desire begin to blur.