Three siblings, Shōma, Kanba and Himari Takakura are living together, despite the fact Himari was given only a few months to live by the doctor. The three visit an aquarium to see the penguins, where Shōma buys her a queen penguin hat. However, Himari collapses and later dies in hospital. As the brothers mourn, they are surprised to see Himari suddenly spring back to life and cured of her condition, possessed by a spirit which has decided to extend her life, though she returns to normal when her penguin hat falls off. The next day, the siblings receive a shipment of frozen things, which are later revealed to be a trio of strange penguins that no one besides them can see. Just then, the hat possesses Himari again, explaining that she has extended her life but in exchange wants the brothers to obtain something known as the Penguin Drum. As Shōma sleeps that night, Kanba ends up kissing Himari as she sleeps.

Shouma tries to dissuade Kanba with no success while Ringo also boards the train, claiming she had learned from the present she got from Himari's friends the secret spell contained into the now lost diary. She activates the spell determined to sacrifice herself to save Himari and the others, but Shouma takes the burden to himself instead while Kanba sacrifices himself to ressurect Himari for good. The terrorist attack is stopped and both Himari and Ringo are found unconsious with no memories about the brothers or everything that happened. The same occurs for Masako whose brother Mario also fully recovers. While hanging with Ringo at her house, Himari finds a message left by Kanba and Shouma and starts crying without knowing the reason why while Shouma and Kanba, in children form, pass in front of her house accompanied by the four penguins.