Plumeau, known as Ochiba in certain localizations, operates as the principal accomplice to antagonist Biscus. Originally running a ramen stand in the human world, Ochiba forges an alliance with Biscus following the latter’s arrival from the magical realm. This partnership creates a Big Bad Duumvirate, with both characters repeatedly collaborating on opportunistic schemes fueled by mutual greed. Ochiba engages actively in Biscus’s get-rich-quick plots, exploiting stolen magical items to target vulnerable townspeople. Their plans consistently collapse due to inherent incompetence and protagonist Lalabel’s interventions.

Ochiba displays a pragmatic, self-serving nature across the series, upholding loyalty to Biscus chiefly for personal advantage rather than authentic devotion. While frequently addressing Biscus as "Sensei" to convey superficial respect, Ochiba occasionally schemes against him when beneficial. This relational pattern endures through most of the narrative.

A pivotal shift occurs in the series finale when both Ochiba and Biscus undergo a Heel–Face Turn. Deprived of their magical powers and moved by human kindness—prompted by townspeople’s compassion during a critical event—they relinquish their villainous ambitions. Having lost their magical abilities, the pair abandons crime and embarks on a shared journey of self-discovery and redemption as ordinary humans.