Itsuki Kiriyama is the serious and by-the-book vice-captain of Ionodai High School's skate-leading team. He possesses steel blue hair falling across his right cheek, the rest swept behind his left ear, complemented by blue eyes and oval glasses. His standard outfit is the fully zipped Ionodai High jacket, matching track pants, a white t-shirt, and white and blue sneakers.

Emphasizing proper conduct and manners, his stubborn confidence in his methods causes frequent clashes and frustration with Kensei Maeshima. Itsuki's reluctance to compromise requires persuasion from team captain Shotaro Terauchi to meet Kensei halfway for team cohesion, though he struggles awkwardly with these efforts.

Itsuki shares a past with Kensei, having skated together in elementary school. Their relationship fractured after Kensei abandoned figure skating, leading to a cold reunion in high school. Convinced Kensei would quit again and jeopardize the team Shotaro sacrificed for, Itsuki initially rejects Kensei's attempt to join. Pressured by Shotaro, he reluctantly accepts Kensei and Hayato as provisional members. However, after observing Kensei deviate from training, Itsuki bans him. Shotaro and Hayato challenge this decision to a three-person match: victory earns Kensei and Hayato full membership, defeat requires them to leave. Following the match, Itsuki remains wary of Kensei's impact on team stability.

During Grand Prix training camp, friction with Kensei resurfaces, again requiring Shotaro's intervention to foster cooperation. Itsuki gradually works towards accommodating Kensei's intuitive style while maintaining his own methodical approach.

Outside skating, he demonstrates skill in art, seen working on an assignment during lunch, and openly acknowledges difficulty with technology. His given name means "tree" (樹), while his surname combines "paulownia" (桐) and "mountain" (山).