Takeshi Kitamaki's life was already a chaotic blend of school and managing his famous idol younger sister, Ayumi, and her two bandmates. He thought he had a handle on things, but his world is turned upside down when he's forced to take in two cousins he hasn't seen since childhood, Azuwa and Inoue. The surprise doesn't end there; his cousins turn out to be superstar K-Pop idols.

Their arrival transforms his home into a battlefield. The hyperactive Inoue and the fiery tsundere Azuwa are both determined to win his affection, sparking an immediate and intense rivalry with the equally possessive Ayumi. Caught between his sister, his friends, and now his idol cousins, Takeshi's calm and orderly life is officially over. He must now navigate a new reality filled with jealousy, chaotic antics, and a constant war for his attention, turning his everyday existence into a miserable yet hilarious romantic comedy.