He was the fastest runner of the track club, prior to Riku Hayata joining as he looked up to him. One morning during practice, he and Riku decided to race, but Riku carelessly tossed the peel of a banana he had for breakfast, and he stepped on it, spraining his ankle. Although Riku felt strongly guilty, Shu would remain nice to him and not upbraid him. However, Riku’s guilt caused a disembodied spirit of himself, continuously crying and apologizing to Shu at his room, and it created a disembodied spirit of Shu, filled with regret over stepping on the peel, as he grew tired of dealing with the wailing spirit day and night and stressful from not being able to tell Riku, who would continuously cause Riku to triple by grabbing his ankle, whenever he runs on the track.
Worried about Riku, Shu sought Rinne, who would show Riku his own spirit, and the two eventually apologize to each other, causing the disembodied spirits of both to vanish.