From the time they were toddlers, Maki Takano, Ryo Arayama, Mei Sonokura, and Natsume Muroki have been locked inside a school for gifted individuals. The school enforces a strict "no going outside" policy and has a rigorous educational system. Despite the oppressive rules, the four live comfortable lives and hang on to the hope they will be guaranteed success once they graduate. However, everything changes when a new girl, Kiriko Hinatsu, shows up at the academy.

After seeing Kiriko, Maki believes to have met her before, but everyone including his friends claim to not remember her. Questioning his memory, Maki confronts Kiriko who reveals she was a former student who had escaped. She further divulges the school is an experimental facility that tests memory-altering medications and other various drugs on the students.

Now aware of the truth, Maki is asked by Kiriko to help her break out again and to come with her, but he is hesitant to take her up on her offer. Leaving means he will finally be able to go outside and see the world he had been kept away from for so long; however, he will lose the safety and opportunities he has been promised. For the sake of his future and his friends, Maki must decide what is more important: freedom in an unknown and chaotic world or comfort in a secure and restrictive cage.