Guyver

Sho and his friend, Tetsuro, stumble upon a strange orb-like mechanism, the Guyver Unit, in the woods. It physically bonds with Sho and turns him into the alien soldier, Guyver. His mission is to protect the Guyver Unit from the Japanese corporation known as Chronos. They are after it and two other units just like it. To retrieve the object, they send out vicious monsters known as Zoanoids. So no one is safe in Sho's life; not even himself.

Note:
Because of the way Viz ordered their chapters, chapter numbers don't match up but chapters 19 and 20 aren't missing.