Taiju Nakano frequents a cosplay café where Shiori Adachi works, initially appearing as an enthusiastic female admirer of Shiori’s princess-themed attire. This façade conceals Taiju’s true gender, later exposed when they forcefully intervene to shield Shiori from a spiked drink during a duel, revealing a fiercely protective and assertive nature that contrasts their earlier submissive desire to become Shiori’s "slave" via the SCM device.

Taiju challenges Shiori to an SCM duel framed as a contest for ownership, tasking each with attracting male patrons’ spending. Though claiming to wish for defeat, Taiju’s tactical maneuvers—including neutralizing threats against Shiori—hint at calculated motives. After Shiori loses and falls under Zenichi Bunkyō’s control, Taiju retreats but eventually allies with Julia Katsushika, bargaining to duel Julia in exchange for aid in rescuing Shiori.

The rescue culminates in Zenichi’s unexpected defeat by Zushiōmaru, a dog equipped with an SCM, underscoring Taiju’s indirect influence in shifting power balances. While Taiju’s origins and deeper motivations remain unexplored, their alliances and confrontations—marked by adaptability to the SCM game’s brutality—blend strategic deception, opportunistic maneuvering, and an underlying drive to protect. These actions define Taiju’s role within the narrative’s immediate conflicts, leaving long-term implications unaddressed.