Back in Middle School, where he attended literature club, he was in love with Mayu, who also was in love with him. On graduation day, her best friend Beniko Yukide asked him to meet her behind the school building so she would confess to him, but Mayu found him before and in her embarrassment accidentally knocked him out by shoving him into a tree. When Shin woke up, he found that the second button of his uniform was gone. Later, Beniko died in an accident, and he and Mayu would date.
A month later, he felt a strange heaviness in his chest and sought Rinne, who revealed the numerous middle school buttons on his second button. After revealing their past, he and Mayu meet the spirit of Beniko who reveals her motive and passes on after accidentally knocking him out by showing him into a tree as well.