Yasunori Kuroki, a talented oboist, joins the R☆S Orchestra during the story's Japanese phase. Witnessing Megumi Noda's piano performance sparks strong feelings within him; he perceives her as pure and simplistic, unaware of her chaotic personal habits and lack of domestic skills. This attraction colors his focus, especially during his inaugural solo performance for the R☆S Orchestra under Shinichi Chiaki's direction.

Discovering Nodame's true nature and her relationship with Chiaki causes Kuroki significant distraction and emotional disappointment. He eventually moves past this, forging a supportive friendship with both Nodame and Chiaki. His professional dedication drives him to pursue further musical studies alongside them in Paris.

In Paris, Kuroki struggles profoundly with the cultural, linguistic, and social transition. His naturally quiet, reserved, and phlegmatic personality—dubbed "samurai-like" by former R☆S peers—hinders his ability to socialize easily. This demeanor draws the mocking attention of Tatiana "Tanya" Vishneva, a Russian conservatoire student, who labels him "Glauque" (a French term implying a dark, depressing, or bluish-green quality). Their initial friction gradually transforms into mutual understanding and blossoms into a romantic relationship.

Professionally, Kuroki becomes part of the Roux-Marlet Orchestra in Paris, conducted by Chiaki. His dedication to the oboe is intense, marked by meticulous reed craftsmanship and a belief that greater technical mastery directly heightens performance joy. His bond with Tanya deepens significantly, culminating in a committed relationship. By the series' conclusion, they are an established couple, and Kuroki has proposed marriage to Tanya.