Himari Takakura passes away after going out on a trip with her brothers, twins Kanba and Shoma. She was, however, miraculously saved by a spirit in a penguin-shaped hat. In return for her extended life, the twins must search for an item known as the Penguin Drum with the aid of three penguins, which are visible only to the siblings.
Once you make a decision, does the universe conspire to make it happen? Is destiny a matter of chance, a matter of choice, or the complex outcome of thousands of warring strands of fate? All twins Kanba and Shouma know is that when their terminally ill sister Himari collapses at the aquarium, her death is somehow temporarily reversed by the penguin hat that she had asked for. It's a provisional resurrection, however, and it comes at a price: to keep Himari alive they need to find the mysterious Penguin Drum. In order to do that, they must first find the links to a complex interlocking chain of riddles that has wrapped around their entire existence, and unravel the knots that tie them to mystifying diary and a baffling string of strangers and semi-acquaintances who all have their own secrets, agendas, and "survival strategies." And in order for Himari to live, someone else's chosen destiny will have to change.