Kei Saijo serves as an operative for the clandestine Phoenix Group, which hunts wolf-men to steal their immortality for world domination. His assignments include brutal tactics like drugging and raping high school teacher Akiko Aoshika to lure the immortal Akira Inugami into captivity. After Phoenix Group superiors betray and abandon him, Saijo survives and defects to Japanese Cabinet Intelligence. His loyalty remains purely self-interested, focused on avenging his betrayal rather than supporting any faction. Within intelligence circles, he aids in extreme medical torture experiments—invasive procedures designed to extract and transfer Akira Inugami's regenerative blood for supersoldier creation. Saijo exhibits no moral growth or redemption; his actions persistently prioritize opportunism and vengeance. His unresolved fate lingers amid the ongoing conflict between the Phoenix Group, Japanese intelligence, and immortal factions.