Ageha Shiraishi has been sentenced to death, suspected of murdering her four roommates. In her prison cell as she awaits her execution, she tells her warden, Kyousuke, that she is innocent and that she did not commit murder. Kyousuke does some research, but finds that she is still guilty. Upon his return, he finds his superior tied up and stripped. After setting her free, he finds out that he has been tricked, and it was Ageha in disguise.

Ageha can impersonate anyone to the finest detail, whether it be hair color, habits, or even voice. She becomes the first fugitive of the Talsis Prison and she declares that she will find the real culprit. Kyousuke now only has one clue, which is "the Ageha" (swallowtail butterfly) tattoo on Ageha's back. The chase between the characters involved begins as they move to grasp the truth!