Brothers Kanba and Shouma deeply love their terminally ill younger sister, Himari, and are unprepared for the prospect of losing her. They are certainly not ready for a family outing to the aquarium, a place holding many of Himari's cherished memories, to abruptly turn tragic when she collapses and passes away. However, what follows defies the siblings' wildest expectations—as Himari miraculously comes back from the dead, wearing a penguin-shaped hat, and joined by some new magical friends!