Jin Hyuuga is the main pilot of Ken-oh, the core unit forming the combined robot Raijin-Oh and its upgraded form God Raijin-Oh. He attends Hinobori Elementary School as a fifth-grade student in Class 5-3, a class that transforms into the Earth Defense Class command center. His family runs the Hyuga Store sake shop, which also serves as their home; Jin's room is situated above the shop. He has a cousin named Youtarou Hyuga.

Jin displays a brash, hot-blooded personality coupled with a strong sense of justice. He demonstrates athletic excellence but shows dismal academic performance and avoids studying. He frequently clashes with class representative Maria Shiratori, though they share a bond of mutual trust. Jin harbors a crippling fear of needles, a vulnerability exploited by syringe-themed monsters. While his impulsiveness can lead to insensitivity, he readily acknowledges his mistakes and offers apologies when confronted.

Operating Ken-oh through a motion-capture system, Jin's physical movements translate directly into the mecha's actions, enabling creative combat maneuvers against the Jaaku Empire's Evil Beasts. His role continues when Bakuryu-oh, an auxiliary dragon mecha unearthed beneath the school, combines with Raijin-Oh to create the more powerful God Raijin-Oh; Jin remains the primary pilot in this configuration.

In later battles depicted in OVAs set roughly one year afterward, Jin and the Earth Defense Class have advanced to Class 6-3. They confront a new enemy, Gokudo, a Fifth Dimensional being who has sealed Belzeb on his back. Jin continues piloting God Raijin-Oh against this threat. These OVAs maintain his established character traits and dynamics with classmates, including his arguments with Maria and leadership in combat. One OVA episode features Kouji narrating an Edo-era fictionalization of their adventures, which includes Jin within its reimagined scenario.