Namako-Otoko, occasionally localized as "Sea Slugman," emerges as one of eight animal demons resurrected by Takeshi Onimaru through the Fujin sword’s corrupting influence. Forged from a sea cucumber host body, he carries out Onimaru’s bidding during initial clashes against the swordsman Yaiba Kurogane and his companions. After suffering multiple defeats at Yaiba’s hands, Namako-Otoko abandons Onimaru’s forces alongside Gerozaemon Geroda, a frog demon, defecting to Yaiba’s side during the Eight Demons Arc. Their shift in loyalty proves pivotal in thwarting Onimaru’s demonic onslaught. Upon Onimaru’s defeat and subsequent redemption, the supernatural energies binding Namako-Otoko dissolve. Stripped of his demonic form, he reverts to his original state as a mundane sea cucumber, dwelling peacefully in the Mine family’s backyard pond alongside Gerozaemon, now reduced to an ordinary frog. No subsequent appearances in expanded media are recorded.