Corporal Giroro is a red-colored Keronian and a key member of the Keroro Platoon, holding the rank of corporal in the Keron Army. He is easily identified by the scar running over his left eye, a mark he received in a past clash with Sergeant Keroro. Unlike other Keronians who display a symbol on their belly, Giroro wears a diagonal belt with a rectangular buckle across his torso; this belt is his most treasured possession, as it holds a picture of Natsumi Hinata and serves as a good luck charm and reminder of comrades lost in a war. As a child, he was a typical young Keronian who bore his skull symbol on both his hat and belly and lacked his facial scar.

In terms of personality, Giroro is presented as the most dedicated and soldier-like member of the platoon, frequently becoming irritated by the lazy and unfocused attitudes of his comrades, particularly Sergeant Keroro. This short temper often leads him to physically assault Keroro as a means of motivation. Beneath this gruff and impatient exterior, he is a trustworthy and honorable individual with a strong sense of duty. He is deeply afraid of ghosts and sea cucumbers and cannot consume more than a drop of alcohol without losing consciousness. His only real hobby is polishing and maintaining his extensive collection of weapons.

Giroro’s primary motivation is the invasion of Pekopon, the Keronian name for Earth, a mission he takes very seriously. However, this goal is constantly complicated by his secret, unrequited love for Natsumi Hinata. After arriving at the Hinata household and being effortlessly defeated by Natsumi in combat, he was so impressed by her skills that he decided to spare the family and set up a tent in their backyard, where he now lives. His feelings for Natsumi are a central part of his character; he becomes a "lovesick puppy" in her presence, grows intensely jealous of any potential rivals such as Mutsumi Saburo, and will abandon any invasion plan if it puts her in danger. The photo of Natsumi hidden in his belt buckle is a source of strength for him, and removing the belt leaves him utterly inept as a soldier.

Within the platoon, Giroro has complex relationships with his fellow soldiers. He and Keroro have been friends since childhood, though their current dynamic is marked by Giroro's frustration with Keroro's laziness. He was a close friend to a younger Zeroro, who would later become the ninja-like Dororo, and the two share a unique bond. He despises the platoon's technical expert, Kururu, due to their opposing philosophies of brawn versus brain, though Kururu frequently uses him as a test subject for various experiments. He also has a significant rivalry with his older brother, Garuru, a lieutenant whom he idolized as a child.

Throughout the series, Giroro undergoes several transformations and demonstrates notable abilities. As the platoon's mobile infantry and guerrilla combatant, he is a weapons specialist with a vast arsenal that includes machine guns, bazookas, and missiles, many of which resemble weapons from the Gundam franchise. He can summon these weapons at will using Keron technology and possesses 100% shooting accuracy. On several occasions, his anger, usually triggered by a need to defend Natsumi, sends him into a "combat mode" where his battle power increases dramatically. He has also been the subject of many mishaps, including being split into seven distinct personalities—such as the evil Giroppe and the housewife-like Girocchi—as the result of a failed experiment. Other transformations have included being merged with Natsumi's hand, turned into a liquid, or even temporarily given a human form with blonde hair.