Tetsuji Suwa holds the position of vice director within the Tingarla Aquarium's sales department. His office demeanor remains consistently stern and serious, characterized by a strict approach to employee performance and task assignments. He enforces departmental boundaries firmly, exemplified when correcting Fuuka Miyazawa for overstepping her role. This strictness is driven by unresolved guilt stemming from past animal welfare incidents at another aquarium, where he felt personally responsible for negative outcomes. Before his aquarium career, Suwa worked in banking.

Upon Kukuru Misakino's transfer to Tingarla, Suwa assigns her to the marketing division, reflecting his focus on organizational structure and role specialization. He dubs her "Plankton," a nickname meant to represent her initial small-scale perspective within the aquarium's vast operational ecosystem. His leadership emphasizes accountability and discipline, motivations gradually revealed as tied to his past experiences and a desire to prevent recurring failures, especially concerning animal care under his supervision. This background fundamentally shapes his interactions and management philosophy at Tingarla.

Suwa possesses gray hair, yellow eyes, and an adult appearance, typically seen in professional attire. His significant narrative focus occurs in the latter half of the primary series, specifically within episodes 13–16 and 18–24, where his involvement in Tingarla's operational challenges and interpersonal dynamics becomes prominent. His character development centers solely on his professional journey within the primary series, without documented expansion into spin-offs, films, or other media.