Seto, the ancient Miniature Schnauzer leader of the secret Hills Dogs in Hoppongi Hills' Dog Paradise, oversees operations aiding needy strays while fiercely protecting his dimension's secrecy. He commands potent "Dog Magic," granting fellow dogs temporary human forms to interact with society, the duration tied to their skill. His authority includes enforcing severe penalties, like transforming offenders into monkeys for breaching their haven's secret—a threat used comically but waived when necessary.

His personality merges eccentricity and profound capability. Prone to scatterbrained moments and perverted tendencies, he often makes suggestive remarks towards human women, particularly Aya, and fantasizes about bathing with them or clubbing with Rumi's grandfather. Yet, he commands deep respect as a wise, powerful mentor, especially in crisis. He exhibits grandfatherly kindness and acts as a Team Dad, becoming a surrogate father to Tetsunoshin. Centuries old, he references encounters with figures like the 16th-century daimyo Takeda Shingen and 19th-century Patrasche, implying an age exceeding 400 years. He occasionally works as a human fortune teller.

Seto's role intensifies during the conflict with the antagonistic Shirogane Dogs. Having trained alongside their leader, Neo, at the same magical grounds, he shifts from a laid-back guide to a strategic leader facing existential threats. He endures personal peril, including a near-fatal encounter with Neo that leaves him temporarily presumed dead. His mentorship deepens as he prepares Tetsunoshin for darker challenges, balancing his usual levity with necessary gravitas. He ultimately witnesses Neo's Heel–Face Turn and sacrificial redemption, underscoring his enduring influence across the conflict.