When Natsuki Aizawa was a child, she was kidnapped which left her traumatized. Natsuki grew up relying on her friend Kentaro Yuki. She now studies physics at a university. One day, she meets newly appointed professor Shuya Tatsumi. Afterwards, mysterious events continually happen around Natsuki Aizawa. Shuya is time traveller who travels between the future and the past.