Utsunomiya Takayuki, son of Mitsuki Utsunomiya, becomes Mira Munakata's maternal half-brother following the revelation of Mira's biological parentage. As a third-year student at Hakuou High School, he serves on the student council. His appearance features blonde hair, yellow eyes, and the standard school uniform.

Takayuki first meets Mira on the latter's initial high school day, unlocking a secured gate after Mira arrives late. He consistently demonstrates romantic interest in Mira, repeatedly calling him "cute" and using the affectionate nickname "kitten" (子猫ちゃん, *Koneko-chan*). Outwardly calm and friendly, Takayuki displays directness by openly declaring his attraction to provoke Kazuki Hino's jealousy.

His involvement stems from familial motives. He actively supports his mother Mitsuki's objective to marry Kyousuke Munakata, believing this union would elevate her fame. This agenda drives his attempts to disrupt Kyousuke and Mira's relationship.

Beyond the OVA adaptation covering only the first light novel volume, Takayuki assumes a more substantial role in the broader literary series. The second novel formally introduces him as Mira's third consummated love interest.