This is a story about certain siblings, suddenly-appeared penguins, and the past and the future of this world... The Takakura brothers, Kamba and Syoma, search for PENGUINDRUM by order of a mysterious penguin-shaped hat to save their ill sister Himari. Ringo Oginome keeps realizing that her destiny has been written in a diary. Masako Natsume tries to get her hands on Ringo’s diary to find her new destiny. Keijyu Tabuki and Yuri Tokikago attempt to get back their precious person of fate. All seek the PENGUINDRUM for their own sake and that of someone dear to them. Ten years later... Kamba and Syoma, who rode the train to change fate, momentarily come back from the place their fate took them…
In an age when large-scale natural disasters frequently happen all over the world, when cyborgs and autonomous robots are beginning to appear on the market in technologically advanced nations, and major world powers compete for technology and resources, the divide between rich and poor grows and the future for the poor looks bleak. In this transitional stage, everyone wanders around in a self-indulgent daze and the way out isn't clear... This is the story of how two cybernetically enhanced girls meet.
Although μ's, the defending champions of the school idol tournament, plans to dissolve their group after the graduation of their senior members, they receive news that leads them to holding a concert event! The 9 girls continue to learn and grow in this new and unfamiliar world. What is the last thing that these girls can do as school idols? With the clock ticking, what kind of meaning will the μ's members find in performing the most exciting live performance?
Yuuta has always been close to his elder sisters, Chiyo and Chinatsu. The only man in the house, he falls in love with the caring and affectionate Chiyo; with her well-endowed body and love of cosplay, she gives her brother everything an adolescent boy could dream of. Envious of her siblings' intimate relationship, Chinatsu soon steps in, seeking Yuuta's attention. As a strong-willed and dominant tomboy, she is the exact opposite of Chiyo and starts picking on him and making aggressive sexual advances. With the situation at home changing dramatically, the siblings must find a way to sort out both their private and school lives and establish a compromise between conflicting interests.
Masayuki's parents have gone overseas, leaving him alone in the house. To his surprise, they have hired Sayaka, a fellow student from school, to work as his maid while they are gone. Masayuki wants his life to be peaceful, but alongside Sayaka's affections he also has to fend off the attention of his kohai, his younger aunt, and his aunt's yandere lesbian admirer.
It's finals time, but tests aren't the only things stressing out Yuuta, who's literally being smothered with affection from his beautiful sisters: Chiyoko, who is feminine, caring, and coddles him; and Chinatsu, a strong-willed tomboy who desperately seeks his attention by picking on him. Who will triumph in this sibling love triangle?
