Suzume, 17, lost her mother as a little girl. On her way to school, she meets a mysterious young man. But her curiosity unleashes a calamity that endangers the entire population of Japan, and so Suzume embarks on a journey to set things right.

Alien pods come to Earth and, naturally, start taking over Human Hosts. One such pod only manages to take over one human's, Shin Izumi, right arm. Together they grow and co-exist, all the while the other aliens are making meals of other humans; Shin feels he must put a stop to it all, but his alien, Migi, doesn't see why.