Ryoichi Yoshimori is a university student. His girlfriend Kyoko Sawada is older than him, but he enjoys his time with her. After Ryoichi proposes to his girlfriend, she suddenly disappears one day. Several days later, he finally sees her again, but Kyoko does not have any memory of him. Ryoichi is stunned, but he suspects her memory loss is related to the Kiokuya rumor. A person named Kiokuya is reputed to erase the memories of people. He talks to Chiaki Takaharu, who is a lawyer and attended the same university, about his situation. Ryoichi searches for the cause of Kyoko's memory loss and gets help from childhood friend Maki Kawai, who is also Chiaki's assistant.