Gekisōmaru leads the Swordbot Shinobi Team, ninja-themed Autobots. His name fuses "Gekisō" (dashing/rushing) with the historical Japanese suffix "maru." He transforms from a lion into a ninja robot, with sections of his beast-mode mane detaching to form kunai-style swords. These weapons store on his shoulders or attach to his "Vivit Bute" whip. His lion head becomes his robot chest, and his kabuto helmet transforms into a small rocket or combines with teammates' helmets into larger weapons.

He exhibits fierce combativeness against enemies, frequently leaping into battle with sudden kunai strikes against Predacons, yet shows deep compassion through his bond with the human boy Tobio Fūma. This relationship drives his story: the Shinobi Team awakens in Nagoya Castle when Tobio activates a Legendisc the Predacons sought. Gekisōmaru then establishes an underground base near Tobio's home and formally designates him as their master.

His combination abilities are central. With teammates Hishōmaru (eagle) and Sensuimaru (shark), he forms one of three configurations: GoGekisō (upper section), GoSensui, or GoHishō. After Optimus Exprime arrives on Earth, Gekisōmaru gains the ability to combine with both Optimus and the Samurai Team leader Kenzan, forming the head, shoulders, and arms as DaiGekisō. Electronic features produce unique sounds and lights across his modes, with combined forms activating configuration-specific dialogue and LED effects.

His story involves time-travel missions to retrieve Legendiscs. He accompanies Tobio to historical periods like the era of Tobio's ancestor Kotarō Fūma, aiding in obtaining a Legendisc from Sasuke Sarutobi. During the final battle against Dragotron at Mount Fuji, Tobio and Isami Tatewaki duplicate the Legendiscs' power, enabling Gekisōmaru, the Shinobi and Samurai teams, and Optimus to form DaiGekisō. This combined form defeats Dragotron and seals the Predacons. His Mini-Con partner, Geki, aligns with his bestial alternate mode as a mammoth-bot.