Mike Jiro, originally named Jiro Suzuki, attends the Private Akapera Academy for Music. Severe tone-deafness plagues his singing, rendering it disruptive and positioning him at the bottom of his class. This amusia stems from the "Dragon Key" collar fastened to his neck during infancy, which suppresses his musical abilities and causes his voice to negatively impact listeners. His condition attracts hostility from Dono Wakaoji, the chairman's son, who seeks to expel Jiro and other children from the academy's affiliated St. Deaf Orphanage.

A pivotal shift occurs when Dono Wakaoji's ring accidentally removes Jiro's collar. This erases his tone-deafness and unlocks a transformative ability. Singing now triggers two physical evolutions, morphing his short stature into the handsome, adept vocalist Mike Jiro. This form wields perfect pitch and heightened singing prowess.

Driven by revelations about his past, Jiro embraces the Karaoke Fighter identity. He focuses on refining his newfound voice and tracing his lost parents, whose absence connects to the Dragon Key's mystery. His journey pits him against rival Dono Wakaoji, while he gradually forges a bond with Hime Wakaoji, Dono's initially dismissive sister who later softens toward him. Yoshio Funaki remains his unwavering ally through every trial.