Yuji, Maki's husband's younger brother, comes to stay with the couple for a month for an intensive course at a cram school. Maki is tasked with taking care of Yuji, whom she hasn't seen in a long time. Maki is Kokoro by Yuji's strong back and young scent. Yuji unleashes his youthful sexual desire on Maki , who is Kokoro and willing to do anything for him. Maki is hesitant, but she is able to satisfy her sensuality...