Kana lives in a house where her older brother's wife, Himari, has recently come to live, making it a household of three. With her brother frequently away due to work, Kana spends more time alone with Himari. Himari becomes deeply depressed when she discovers her husband's infidelity shortly after their marriage, and Kana, struggling with her own strained relationship with her brother, finds it hard to talk to him. Later, Kana learns that her boyfriend has also been cheating—with her best friend. As both women face heartbreak, they begin to support each other, rapidly growing closer and forming a new, intimate relationship.