The narrative follows two classmates, Sahoko and Rio, who become friends. Rio suffers from depression and self-harm, and she is not loved by her "family"—comprising her father, stepmother, and stepbrother—while Sahoko appears to be the bright spot in her life. Sahoko also seems to have a mysterious past and does not appear to have a good relationship with her parents; she lives with her aunt. It is also hinted that Sahoko and Rio met once before, when they were much younger...