Yūji Kōsaka, alias "Townsperson A," is a high school student with red, short spiky hair, straight bangs, and soft brown tareme eyes, his slim frame often clad in a casual gakuran, hoodie, and trousers. As Tamaki Kōsaka’s younger brother, he navigates a sibling rivalry defined by her aggressive forehead-crushing reprimands, reactions to his mischievous antics.

He thrives as the protagonist’s loyal best friend and classmate, embodying a perverted yet good-natured jester with a carefree charm. His humor masks a flicker of envy toward the protagonist’s romantic fortunes, though he counters this with relentless, often ill-fated flirtations. Despite hailing from wealth, he proudly hustles as a part-time merchant, driven by a pragmatic love for money.

A self-styled photographer, Yūji wields his camera with a cheeky focus on female subjects, a habit sparking both laughter and chaos. His teasing nature and fleeting romantic pursuits—routinely thwarted by bad luck or meddling peers—underscore his role as a lighthearted troublemaker. Loyalty anchors his relationships: unwavering camaraderie with the protagonist, combative kinship with Tamaki, and transient crushes that dissolve as quickly as they form.

Consistently portrayed across media as a comic-relief fixture, Yūji peppers the narrative with levity and glimpses into the protagonist’s world. His wealthy lineage contrasts with mundane hobbies like shopping and cleaning, grounding him in relatable simplicity. While lacking major growth, his enduring presence as a humorous foil shines through recurring gags—Tamaki’s disciplinary tackles, romantic misadventures ending in slapstick defeat—cementing his role as a stable, laugh-filled constant.