Williams Gin is an artificial lycanthrope engineered through night-gene implantation by an unspecified organization, designed to rival mana users. Born into the noble William family, he failed to awaken mana in childhood and was abandoned in a distant village, replaced by his newborn brother—a societal pattern for mana-deficient nobles facing concealment or exile.

He operates within Guild Grimfice, wielding green anima to manipulate highly durable bandages as weapons and shields, capable of resisting Kufa Vampir’s black blade. Initial enmity toward Kufa, stemming from opposing guild loyalties, shifts when Kufa uncovers Williams’ lycanthropy and coerces his cooperation. Williams falsifies reports to falsely confirm Melida Angel’s paladin mana, shielding her from exposure.

Later, Williams infiltrates Guild Grimfice as a mole for Guild Jack Raven, striking a deal with Father. In exchange, he demands White Night faction membership and intelligence on reversing lycanthropy. This alliance leads him to aid Kufa and students during the biblical exam when Guild Grimfice ambushes them under Mordrew’s directive.

His pragmatic motivations—rooted in seeking acceptance and a cure—drive an unexpected bond with Shenfa Zwitoque. During the Vibria Goat exam, Williams rescues Shenfa, the headmaster, and other students after Kufa summons reinforcements. Shenfa alone shows no fear of his lycanthrope form, dubbing him "Bandage Knight" and offering gratitude, leaving Williams visibly disarmed. His alliances evolve from antagonism to reluctant cooperation, particularly against shared threats like the Necromancer.