Ryoichi Yoshimori is a university student. His girlfriend, Kyoko Sawada is a few years older but the pair don't care as they are deeply in love. After Ryoichi proposes to Kyoko, she suddenly disappears. Several days later, Kyoko re-emerges but claims to have no memory of him. With the help of a classmate/lawyer Chiaki Takaharu and his childhood friend Maki Kawai, Ryoichi attempts to unravel the mystery that may be related to the rumours of a memory erasing individual known as Kiokuya.