On the way to visit Shun, who didn't attend class, Hiroshi and Anna are drawn by a mysterious butterfly and enter the big house “Jail House”. They get lost and wander around the house. Meanwhile, Takuro, Mika and Takeshi, who bullies Shun, enter the “Jail House” to test their courage.

Sana Haitani (Kasumi Yamaya) is a member of an idol group. She's following the dreams of her now deceased older sister who always wanted to become a top idol. Unfortunately, Sana's idol group is disbanded. She is then kidnapped and taken to an uninhabited island. What awaits for her is a card battle. If she wins in the card battle against other kidnapped idol girls, she can become a top idol. But, if Sana loses ... she will die.