Mafuyu Sone is sent to live with her brother Takashi in Tokyo after being caught in a compromising situation at school. However, Takashi's household is soon disrupted by the arrival of Sae Shirai, a girl who has been disowned by her parents and has nowhere else to go. As Takashi struggles to balance his role as a big brother to Sae with his own relationship with Mariko Abe, he finds himself torn between his duties and his own feelings.