WoO (ＷoO（うー）, Ū WoO?) is the only survivor of his species and wandered in space on a comet until he crashed on Earth. There, he met Ai a junior high school 2nd year student who’s school is then attacked by a giant monster, which resulted in her being the lone survivor of the attack after their encounter. WoO develops a strong bond with her saying that he will protect her at any cost. He uses his antennae to connect to electronic devices (mainly a cell phone) to communicate with her. Both are chased by a mysterious organization called SWORD who sees WoO as a threat to humanity. At the same time giant monsters have begun to invade the Earth in search of WoO who must now fight both SWORD and the monsters for his survival.