Max Reed's superior in the CIA, Col. Castle and at least two of his other subordinate agents were secretly working for the Chronos Corporation. He oversaw the attempted extraction of Dr. Tetsu Segawa and the retrieval of the Guyver unit (after which he, apparently, intended to turn right around and return the Guyver to Chronos). However, the operation was bungled by Lisker and his Zoanoid hitmen.
While Lisker searched for the Guyver, Castle tried to keep Max Reed from investigating Chronos by having his two agents follow Reed around the clock (they were both eventually killed in battle with Sean Barker after he obtained the Guyver). Following the demise of Fulton Balcus and nearly every other Zoanoid, Castle approached Striker and offered him "a job."
Exactly what this job was is never revealed as, somewhat annoyingly, neither Col. Castle nor Striker appeared in the first movie's sequel, Guyver 2: Dark Hero. And although both of Castle's subordinate agents were Zoanoids, it is unknown if Castle himself was one.