Miyuki Sakaigawa is a third-year dentistry student at Kamogawa Music College Faculty of Dentistry in Tokyo. He serves as the drummer for the band GYROAXIA, having transitioned from a background as a former kickboxer to drumming specifically to enhance his popularity. His drumming style capitalizes on his natural strength, delivering flashy and impactful rhythms that leave a distinct impression.

Among GYROAXIA's older members, Miyuki maintains a generally stoic personality despite outward appearances, though he shows consistent friendliness toward children and women. He harbors significant hostility toward the band's manager, Kenta Satozuka, due to strong disagreement with Kenta's management policies. While Miyuki admires GYROAXIA's vocalist, Nayuta Asahi, he explicitly rejects Kenta's philosophy that advocates sacrificing humanity for Nayuta's musical advancement.

His surname Sakaigawa combines the characters for "world" (界) and "river" (川), while his given name Miyuki incorporates "deep" (深) and "happiness" or "good luck" (幸). Physically, he has yellow or blonde hair, grey eyes, stands 1.83 meters tall, and weighs 76 kilograms.