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.
In casa Takakura è un giorno di festa: la piccola Himari, gravemente malata, sta meglio e i suoi fratelli maggiori Shoma e Kanba organizzano una gita all'acquario di Ikebukuro. Qui Himari ha un collasso e, nonostante le cure dei medici, muore.
両親のいない高倉家には３人のきょうだいが暮していた。
双子の兄の冠葉と弟の晶馬、そして妹の陽毬。
陽毬は不治の病に冒されており、担当医の鷲塚医師から余命が長くないと宣告される。
数日後、自宅へ帰ってきた陽毬は、兄と一緒に水族館へ行く。
数少ない家族の思い出が残るその場所で、陽毬は不思議なペンギンと目が合う……。
