Narumiya, affectionately dubbed "Mister" or "Old Man," runs the neighborhood yoyo shop. He acts as a steadfast pillar of support for protagonist Shunichi Domoto, extending both moral encouragement and hands-on yoyo expertise. His establishment doubles as a vibrant gathering spot for enthusiasts, where Narumiya cultivates camaraderie and dispenses guidance to budding spinners. His role transcends typical shopkeeping, actively connecting Shunichi with competitive resources and mentorship opportunities.

Narumiya anchors a pivotal thread in the backstory of Kenichi Nakamura, Japan's inaugural Pro Spinner. He crucially shaped Nakamura's trajectory during his prodigious early years, before Nakamura abandoned the sport for want of rivals. This legacy positions Narumiya as a generational conduit, preserving the sport's history and cultural ethos. His shop also drives narrative momentum, unveiling key elements like the Hyper Dragon prototype yoyo that fuels Shunichi's growth.

Throughout the series, Narumiya remains a steadying force. His interactions consistently champion community bonds and the transfer of specialized knowledge, echoing the anime's core themes of mentorship-fueled progress and collective passion for yoyoing.