Tetsushi Sumitomo operates Café Cowbeya, a café renowned for its staff’s revealing uniforms—his original designs tailored to draw otaku patrons. His childhood aspiration to own such an establishment stemmed from a lifelong obsession with provocative cosplay aesthetics. He shares an unorthodox bond with his daughter Minori, the café’s sole employee, who enthusiastically wears his creations and mirrors his fervor for their daring style. Unmoved by conventional parental concerns, he openly takes pride in her striking appearance, emphasizing his disregard for societal norms.

A mutual fascination with cosplay ignites a spirited rivalry with Takaya Murase, culminating in a costume design contest that transitions into mutual admiration. Their competition solidifies a friendship anchored in shared niche interests. Tetsushi’s business ethos and personal passions align seamlessly, as he relentlessly prioritizes his café’s distinctive vision while fostering a space unapologetically embracing eccentricity.

His narrative remains anchored within the original series’ framework, without elaboration in additional media or transformative character arcs.