Love can be obsessive. Like wanting to rip the wings off a butterfly. Chouko has been in love with Taichiro for a long time. Taichiro and Chouko have known each other since childhood. At one point, Taichiro became very candid and told Chouko that he hated her so much that he wanted to kill her. Even so, Chouko's desire toward him never really changed. One day, a senior in her athletics club confessed to her. Filled with burning jealousy, Taichiro also confessed to Chouko. Their insecure, but very obsessive love begins. An extra can be found inside of Yoru Koi.