Haruta Kamijo is a first-year high school student and the childhood friend of Chika Homura. He is known for his perfect outward appearance, characterized by short, slightly spiky blond hair and blue eyes, and is usually seen in his school uniform. Beyond his looks, he possesses a clear and sharp mind. His name contains the character for "spring," and he was born in April, which is the spring season.

In the story, Haruta is a dedicated musician who plays the French horn. Together with Chika, he works to recruit new members for their school's wind ensemble, which is in danger of being shut down. His motivation for this effort is closely tied to his feelings for the band teacher, Mr. Kusakabe, as both he and Chika are attracted to the teacher, which often creates tension between them. Haruta worries about the love triangle he finds himself in with Chika.

Haruta has three older sisters. He and Chika are not only bandmates but also partners in solving the various mysteries and incidents that occur at their school. Regarding his personal development, the available information is limited, but it is noted that he worries about the romantic dynamics with Chika and his teacher. His notable abilities include his intelligence and his talent as a horn player.