Born in Manchukuo, Hideki studied Gōjū-ryū karate and Chinese martial arts under his grandfather during his youth, establishing foundational combat skills and martial philosophy. He initially pursued acting, joining a children's theater company before being scouted by Shintoho Studios. Following the studio's bankruptcy, he abandoned entertainment aspirations to focus on martial arts. At university, he joined the Goju-ryu Karate Club, achieving an undefeated record in 60 fights and winning the All Japan Student Championship.

His traditional karate style emphasized technical precision but lacked full-contact experience. Entering kickboxing competition to prove karate's superiority with an arrogant mindset, he suffered a devastating loss to a modern kickboxing practitioner in a critical match. This resulted in severe injuries—over 25 bruises and 16 knockdowns—leaving him physically incapacitated, emotionally disheartened, and comatose.

After recovery, Hideki transformed under trainer Endo's guidance. Recognizing his traditional approach's limitations, he dedicated himself to mastering kickboxing, incorporating techniques like the "vacuum jump knee kick" and "kick before jump." His rigorous retraining involved physical conditioning and strategic adaptation to full-contact combat. This marked a shift from arrogance to disciplined perseverance, driven by regaining honor in the ring.

His journey from defeat to mastery unfolded through humility and technical evolution, culminating in high-impact offensive techniques that became signature elements of his fighting style.