It is quite clear to Terui Chiaki that her classmate, Ajikawa Yoshio, has a crush on her. In her view, he is entirely unsuitable as a boyfriend, and even if he were, Chiaki already has one. Their enigmatic teacher, Mr. Yamada, observes this dynamic between the two students and proposes an experiment. He possesses the ability to duplicate people and objects, which he uses on Chiaki to create a copy. This duplicate, however, lacks any memory of her boyfriend. Yoshio will pursue the Chiaki copy, named Koaki, attempting to make her fall in love with him. After a set period, the copy and the original will be merged, and whichever affection proves stronger—between her current boyfriend and Yoshio—will overwrite all other emotions. Thus, the love experiment commences. Both Chiaki and Koaki, being the same person, believe Yoshio has no chance whatsoever, yet as days pass, certain feelings start to surface.