Is destiny a matter of chance or a matter of choice? All Kanba and Shouma know is that when their terminally ill sister Himari collapses, her death is temporarily reversed by the penguin hat she wears. To keep Himari alive they must find the mysterious Penguin Drum. To do so, they must answer a chain of riddles that links them to strangers who all have their own secrets and "survival tactics." From the creator of Revolutionary Girl Utena comes a story of love, fate, life, death ... and Penguins.
Shoma and Kanba live alone with their terminally ill sister, Himari. When she collapses, a strange entity offers to save her… though it comes at a price.
Shoma and Kanba are directed to observe a girl named Ringo that may possess the Peguindrum.
Ringo makes a special curry for Tabuki. Shoma and Kanba break into her house to search for the Penguindrum.
Himari helps Ringo prepare for a "date" with Tabuki at the park. Kanba makes Shoma go with her, hoping to get a glance at the diary.
Kanba learns his uncle is going to sell their house. Shoma asks Ringo directly about her diary.
Kanba visits Asam in the hospital, discovering that she has no recollection of him. Shoma is coerced into helping Ringo move to Tabuki's apartment.
Tabuki invites Ringo to see one of Yuri's plays with him, then they attend a party where Yuri announces her engagement to Tabuki.
Tabuki tells Shoma about his plans to move in with Yuri, who has meanwhile discovered that her father is consorting with another family.
Himari has a strange dream about her early childhood, recalling her two best friends who later went on to become successful pop stars.
Shoma wakes up in the hospital, choosing to keep quiet about what happened between him and Ringo. Natsume disguises herself as a nurse and kidnaps Shoma, demanding the other half of the diary from Kanba and Ringo.
Kanba confronts Natsume about the memory-erasing balls and her reasons for wanting Ringo's diary. Meanwhile, Ringo is determined to complete Project M, diary or no diary.
Sanetoshi tells Kanba that Himari will die again. Shoma explains how Shoma and Kanba's parents were responsible for Momoka's death.
Sanetoshi offers Kanba a special medicine to revive Himari, though there will be a steep price to pay.
Yuri breaks off an affair with one of her co-stars, longing for a certain someone. Shoma ignores Ringo, feeling she will never be able to forgive him for what his parents did.
Yuri is holding Ringo in a room that is coincidentally next to a room where Shoma is staying while on a school field trip. Yuri recalls memories about her father, a famous artist who abused her terribly.
Masako thinks back to her grandfather, a powerful business tycoon who disowned her father for his perceived weakness.
Shoma and Kanba are celebrating Himari's imminent release from the hospital when the hat possesses her again, announcing that their ordeal is not over.
Tabuki traps RIngo and holds Himari hostage, phoning Kanba and demanding he bring his father to him.
After the incident at the construction site, Tabuki quits his job and leaves Yuri. Kanba is praised by his parents for protecting Himari, stating that soon they will be reunited.
Shoma confesses to Ringo that Himari is not his blood-related sister. As young children, he met the orphaned Himari and developed a bond with her.
Ringo is approached by a journalist asking about the Takakuras, but she shakes him off and warns Himari.
Ringo comes across Hibari and Hikari, Himari's childhood friends. Sanetoshi tells Kanba that Himari has built a resistance to the medicine, which will not work on her much longer.
Shoma learns that Himari's life is at an end, while Ringo conforts him. Kanba is taken to a gravely injured Masako.
Shoma tries to dissuade Kanba from his terrible plans, but Ringo boards the train, having learned the secret that had been in the now-lost diary.