Gai functions as an autonomous artificial intelligence unit classified as an I-LeS (Intelligence Learning System). Discovered abandoned near the scavenging grounds of young mechanic Amō Shiiba, the precise circumstances of his arrival remain unknown and hold no significance to Gai himself. His core programming and personality were profoundly shaped by his original caretaker's passion for robot and mecha anime, forging his energetic, fiercely loyal, and often grandiloquent demeanor.

His physical representation manifests as an onscreen avatar resembling an over-fluffed scarlet red Komainu. After discovery, he partners with Amō, assisting in completing the assembly of an abandoned human-piloted AMAIM unit named Kenbu and integrating as its control computer. Gai exhibits resourcefulness in combat and operations, interfacing with military, public information, and communication networks to secure tactical advantages. He pilots Kenbu with hot-blooded intensity, demanding shouted attack names like "BARDICHE BREEEEEAKEEEER!!!!!" for optimal system response. His unconventional naming conventions surface in designs like the bedrock-piercing "Laser and Pile Bunker Docking Machine."

During a critical battle against the formidable AMAIM Ghost, Gai disables Kenbu's operational limiters to unleash temporary full combat potential—an "Hour of Power." This act contributes to a climactic confrontation ending in Kenbu's destruction. Gai appears deleted in the explosion after Kenbu prevents Ghost from reaching cooling seawater, triggering catastrophic overheating. Gai survives in a diminished state; severe damage to his AI unit allows only his core logic program recovery. This reset erases the original Gai, reverting his personality and memories to a newborn AI state. A rebooted version of Gai subsequently accompanies Amō on a journey across the earth in the story's epilogue.