An older brother who really wants to get along with his sister, Miiro. A younger sister who hates her brother who always voyeurs and confesses. One day, Miiro, who broke up with her boyfriend, accepts her brother's confession, saying, "If it's only for a month ...". Without knowing that it triggered an irreversible forbidden relationship. An incest life that can not be said to parents that started from that day. Gradually, Miiro becomes a captive of her brother and cannot live without her brother. After a while, my brother who left home suddenly came back with his fiancé ... At that time, Miiroha ...