Rio Kikyō is a first-year university student enrolled in Political Economics. Recognized as a child prodigy from a young age, he excelled academically, athletically, and musically. His primary ambition was baseball, aiming for the Koshien tournament, but a severe injury just before participating forced him to abandon the sport completely. This pivotal event significantly shaped his outlook, leading him to conceal his emotions and maintain a detached, outwardly apathetic demeanor. He generally avoids forming close relationships. However, he made an exception when approached by Yuto Goryo to join the band Argonavis as their keyboardist, demonstrating full commitment and dedication to the band once involved.

His family background includes being the son of the director of a prominent confectionery company based in Hakodate. After transferring to Kamogawa Music College, he shares the Faculty of Political Science and Economics with Misaki Goto. Within Argonavis's Four-Temperament Ensemble framework, his personality is melancholic. His reserved nature and reluctance to express feelings stem directly from the disappointment and abrupt end of his baseball dreams. Despite this guarded exterior, he possesses an underlying willingness to support others who reach out to him genuinely, as seen in his response to Yuto's invitation and his subsequent wholehearted effort within the band.