Onuki earned a Bachelor of Science from Towson University and Master of Science in Applied Physiology and Kinesiology from University of Florida (UF). After graduating from UF, Onuki joined the Texas Rangers (MLB) as a season intern, then was hired by the Medical Center of Arlington as a head athletic trainer for the Fort Worth Flyers (NBA D-League). During 2006-2007 season, he was selected as the Eastern team athletic trainer for the inaugural D-League All-Star Game in Las Vegas. After serving in athletic training/sports medicine rehabilitation for Professional Physical Therapy in New York, Onuki returned to Texas joining Texas Metroplex Institute (TMI) of Sports Medicine. While at TMI, he was responsible for coordinating the physical therapy rehab, baseball conditioning program, and pitching biomechanical analysis laboratory. In 2012, Onuki joined the Arizona Diamondbacks as a minor league athletic trainer and served Yakima (Rookie A) and South Bend (Low A).
Onuki was introduced to PRI through Kenny Ishii, current PRI faculty, during 2010. Since then he is passionate about finding ways to implement Postural Restoration science for general population injury prevention while applying PRI concepts into baseball injury prevention. Onuki completed the Postural Restoration Trained (PRT) credentialing program in January 2016. He envisions to improve the sports medicine environment for both athletic trainers and athletes in Japan, especially in youth baseball populations. Onuki and his wife Jessamyn reside in Kyoto, Japan with their daughters, Sumire and Akira.