Miko Yahiko is a 23-year-old keirin cyclist competing at Niigata Prefecture's Yahiko Velodrome. Standing 158 cm tall with light pink hair and orange eyes, she maintains a youthful appearance reflecting her past. Before cycling, she was the center of a local underground idol group in Niigata. After the group disbanded due to internal issues, she sought financial independence through a new career. She founded the "Tackle Channel," a fan project supporting top racers like Remu Tachikawa and Tsutsuji Kurume. Meetups through this channel inspired her and future cyclists, including Izumi Itou, to pursue the sport professionally. She ended channel activities upon committing to racing.

Her personality blends confidence, outspokenness, and approachability, retaining a strong drive to stand out and win, channeling her idol past into competition. Initially struggling to translate this ambition into results, she actively seeks advice to improve. Enrolled in the RINKAI LEAGUE's L14 class, she faced early setbacks, failing initial short and long distance time trials. This required training under the "blue cap" designation for athletes needing improvement. Mentorship from established racers Miyako Mukomachi and Tsubaki Matsuyama proved pivotal. They taught her the "marking" strategy—drafting closely behind a leader before a timed overtake—letting her leverage her strengths effectively.

She signed her racing bike's frame with her idol autograph, symbolizing the connection between her past and present identities. Her relationships include a friendship with fellow cyclist Izumi Itou, who also transitioned from fan to athlete. She respects and learns from veterans Miyako Mukomachi and Tsubaki Matsuyama, while her Tackle Channel past connected her to figures like Remu Tachikawa and Tsutsuji Kurume.