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.

The Takakura siblings are enjoying Takoyaki together and happy with the news that Himari will soon be released from hospital when the magic hat posesses Himari again for another Survival Strategy meeting with her brothers and insists that their ordeal will not be over until the Penguin-Drum is retrieved. Meanwhile, Yuri and Tabuki reminisces about their childhood days with Momoka and while Yuri is unable to forgive the siblings for their parents' crime, Tabuki tries to dissuade her. In the next day, Himari leaves by herself with Ringo for shopping much to Kanba and Shouma's despair as they are informed that she must take another dose of her medicine before sunset. While the brothers look for Himari, Ringo receives a call from Yuri who invites her and Himari for a meeting. Yuri waits for Himari, but is intercepted by Masako instead, and the two start fighting for the two halves of the diary, while Himari and Ringo are approached by Tabuki who invites them to a construction site where he claims he will finally bring punishment to the Takakura family.

On the day of the terrorist attack, 16 years before, Sanetoshi is contronted by Momoka who was determined to stop him and while her spirit ends up split in two with each half becoming the penguin hats used by Himari and Mario, his is divided into the two black rabbits that always accompany him. Back to the present, Shouma is informed that Himari's life is at its end and Ringo conforts him while Kanba is taken by Sanetoshi to a gravely injured Masako and brings her from the dead before his eyes. Despite Masako's pleas, Kanba leaves with Sanetoshi to continue his plan, carrying her half of the diary with himself. Shouma sees a vision of Himari asking him to stop Kanba, and when his brother comes to fetch her, he is shot unconsious by him with a penguin bullet. Ringo is called by Kanba to the aquarium and a bomb explodes knocking her out. Sanetoshi watches her struggling to stop her half of the diary from being burned out and after she fails, he has Kanba burn the other half. Shouma wakes up and manages to reach Kanba determined to stop his plans.

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.