Rikimaru shares the vital duty of protecting Konpei Island's last surviving dragon, Pochi, with his fellow guardian Kosuke. Their daily life revolves around safeguarding the dragon and providing care, including delivering baskets of oranges for sustenance. The dragons of Konpei Island, hunted nearly to extinction, bear a precious jewel on their foreheads, making them targets for exploitation and inextricably linking the islanders' fate to their survival.

When a researcher arrives from Tokyo to study Pochi, Rikimaru helps host her visit. This coincides with an attack by hostile forces led by collector Yamada Daihachirou, who seeks to steal the dragon's jewel. Accompanied by mercenaries and mechanized threats like a mechanical sumo wrestler, they initiate a conflict. Rikimaru confronts these intruders directly, including the skilled fighter Michael Commando, defending Pochi and fighting to reclaim the jewel.

Rikimaru and Kosuke operate as partners, their relationship defined by shared duties and cooperative efforts to protect both the dragon and the island's balance. They coordinate their guardianship from a simple dwelling on the island. During the researcher's stay, Rikimaru's interactions reveal aspects of island life, such as directing her to basic facilities like a river for bathing while cautioning about natural hazards.