When four brothers lived together in their family home, the eldest suddenly took advantage of the second brother's girlfriend while drunk, causing the second brother to experience devastating betrayal. Later, the second brother meets a new girlfriend, but under pressure from all the brothers who demand he "let them fuck her," a rule is established where they all share her. Unaware of this arrangement, Ayaka Tomoda gets caught up in the situation, struggling with how to live her life. A story woven from the brothers' shifting emotions and Ayaka's inner turmoil.