Oicho is one of the street children surviving in the forbidden district alongside Sachio, Bonjiri, and Santa. These orphans steal mechanical parts to trade for necessities like red candy. In the first season, Oicho remains largely a background figure with little dialogue or involvement in the main story.

Her role grows substantially in the second season, *Nomad*. After Nanbu's death and Joe's departure fracture their group, Oicho apprentices with the mechanic Abuhachi. Working in his shop, she develops engineering skills, maintaining and developing gear, marking a shift from scavenging to a stable vocation.

Oicho becomes crucial in voicing the perspective of those Joe abandoned. When discussions surface about Joe's abrupt exit five years prior—specifically Sachio's grief-stricken command for Joe to leave after Nanbu died—Oicho categorically rejects this as justification. She argues that any adult taking a child's emotional outburst so literally to justify abandonment cannot be trusted. This position highlights her protective instincts toward Sachio and her maturation into someone holding others accountable.

Her presence in the narrative helps explore the consequences of Joe's choices on his found family. Oicho's journey demonstrates resilience and practical skill-building following the group's separation.