Mogumogu is a mole and one of three primary antagonists alongside Black Bat and Takochu. He belongs to a group residing in a cave near Chirorin Village, engaging in petty theft against residents as part of their comedic schemes. Mogumogu stands out for his notably gentler and more oblivious nature compared to his companions, serving as the least malicious member of the trio.

Within the group, Mogumogu typically follows Black Bat's lead but occasionally participates in covert thefts with Takochu, hiding loot from Black Bat due to expectations of their leader's selfishness. Despite their antagonistic role, Mogumogu's actions lack genuine malice, consistent with the show's non-threatening villain portrayal. His schemes include attempts to steal the village school bell and later food supplies.

Mogumogu's story intertwines with Black Bat's redemption arc, influenced by the persistent kindness of Miss Apple, which gradually affects the group. During a forest fire crisis, Black Bat performs a dramatic rescue of a trapped child and saves the school bell, prompting the village to offer the trio a chance at reform. However, after another villager falsely accuses Black Bat, Mogumogu demonstrates unwavering loyalty. He chooses to depart Chirorin Village with Black Bat and Takochu rather than stay without their leader, explicitly affirming his commitment to remain with Black Bat despite the villagers' forgiveness.

Mogumogu's arc concludes as he leaves alongside Black Bat and Takochu, verbally expressing an intention to return someday, symbolizing an unresolved yet hopeful trajectory toward potential future redemption.