Jay, whose real name is Junior, commands V-Stealth Robo as its Robo Master. Originally an agent for the antagonistic organization DISASTER under Kaiser-G, he unleashed havoc across Japan using destructive robots called Gara-goros. His past traces to a catastrophic space shuttle incident during infancy: electromagnetic interference likely caused the craft's failure during Earth re-entry while carrying his parents and crew. As the sole survivor, Jay ejected in an escape pod and was discovered by a lunar exploration team. He later lived in an orphanage before DISASTER captured, brainwashed, and trained him as a warrior.

Like MRR comrade Taiyo Ozora, Jay possesses the innate "survivor natural" ability to sense imminent danger. Taiyo and pivotal rescue missions catalyzed Jay’s defection from DISASTER and reformation. During an attack orchestrated by DISASTER Colonel Hazard at an amusement park observation tower—trapping civilians and MRR cadets including Lin and Jun—Jay intervened. Assisted by Taiyo and piloting V-Stealth Robo, he evacuated the hostages and destroyed Hazard’s BL Drill Robo. This choice to protect over seeking vengeance secured his acceptance into Machine Robo Rescue.

Within MRR, Jay spearheads the specialized Stealth team with V-Stealth Robo, executing combat operations across air, land, and space. The team is marked by violet coloring and an emblem of V-Stealth Robo’s vehicle mode streaked with lightning. Jay’s combat expertise became vital to MRR’s missions. After integration, he and fellow cadet Kai Kitazawa were assigned to space operations under International Hyper Rescue, residing on a satellite.