Tatsuya Tanaka, a junior high school student, travels alone during a school trip from Fukuoka to Tokyo and comes to Shibuya in search of his childhood friend Haruka Imamura, who is five years older than him. However, he gets lost in an unfamiliar place and collapses from hunger. Ai, a mysterious heron master, helped Tatsuya. Tatsuya and Ai search for Haruka and find the store where she works...