When the comet Dream Suisei, which visits Earth only once every hundred years, passes overhead, everyone on Earth experiences the same dream of a foreign world. Melonpanna saves an egg from being crushed and, upon waking, discovers that the egg has followed her home. The egg hatches a kitten, which she names Nyanii and begins to care for. However, they soon learn that Nyanii must return to Dream Suisei, and if she does not, she will vanish. Melonpanna grapples with the looming goodbyes, but the true crisis begins when Baikinman inadvertently awakens the evil monster Muuma.