Kouji Hoshiyama, ninth student in Hinobori Academy’s Class 5-3, belongs to the Earth Defense Class and commands the lion-shaped mecha Jyu-Oh. As the primary pilot and specialist overseeing power control and weapon systems for the combined Raijin-Oh and God Raijin-Oh robots, he begins as timid yet steadily cultivates bravery without losing his inherent kindness. Positioned as the group’s non-confrontational "Heart," he mediates between the fiery Jin and disciplined Asuka, stabilizing their dynamic.

Beyond combat, Kouji occasionally steps into a narrative role, offering Greek Chorus-style insights to clarify unfolding events. A steadfast believer in UFOs and the occult, these passions seep into his interactions and unconventional problem-solving methods. Though initially hesitant to fight, he rises to adversity with resilience, mirroring the "Cowardly Lion" archetype as he evolves from apprehension to unwavering commitment in Earth’s defense.

His background emphasizes familial and peer connections, though specifics remain undisclosed. Growth emerges through collaborative triumphs, where his technical expertise and steady composure bolster the team’s strategies. His journey remains anchored to incremental confidence forged in high-stakes teamwork, as documented in the television series.