Isahaya Ichi has reunited with her former classmate, Masaki Makuhito, a man who was once her partner in a school experiment called "Gene Bride" that matched people based on DNA. Now, she can't stop thinking about her friend, Edo Enami, who went to the same school as them. Longing to catch up with Enami, Ichi asks Makuhito for help, but on the day they meet up, they encounter a teenage girl with the same face and name as Ichi. Who is this mysterious girl? Finally, the truth of Ichi and Enami's school life is brought to light!