Seba Suuchan serves as Midori Okuike's butler and Hand Shaker partner. His background prior to this role remains largely unknown, though Reijiro Araki observes Seba appears "too rough to be a butler," hinting at a contrasting past. Seba initially supported Midori's childhood wish to aid the Okuike Group, utilizing his ability to extract precious metals from the Ziggurat dimension through self-inflicted wounds. This ability gradually deteriorated Midori's health.

When Midori's father began forcibly extracting the metals, endangering Midori's life, Seba intervened. He killed Midori's father and his associates to rescue Midori, an act that redefined his loyalty. Following this event, Seba dedicated himself entirely to Midori's well-being and objectives, including Midori's later pursuit of Yukiya Araki's powers as an irregular Hand Shaker.

Throughout the series, Seba remains steadfast in his support of Midori's plans, acting as both protector and enforcer. He participates in battles within the Ziggurat dimension alongside Midori, leveraging their Hand Shaker partnership. After Yukiya uses a wish to heal Midori in the finale, Seba continues his service as Midori abandons his pursuit of Yukiya.

Seba stands 188 cm tall and possesses distinctive facial hair. The name "Seba" is an alias; he previously worked as a hitman in the criminal underworld, though specific details about this period are undisclosed.