Hironaka made his professional mixed martial arts debut in 2001 for the Shooto promotion and compiled a record of 10-2 with notable wins over Nick Diaz, Ryan Schultz, and Renato Verissimo before being signed by the UFC.
In his next appearance at UFC Fight Night 9, Hironaka defeated Forrest Petz via unanimous decision.
Hironaka then fought Thiago Alves at UFC Fight Night 11 and was defeated via TKO in the second round.
In his first fight since his release from the UFC, Hironaka defeated Motoki Miyazawa at Dream 5 via TKO due to a cut.
Hironaka won via unanimous decision, and then defended his title against Giovani Diniz via first-round TKO.