クルル曹長, Sergeant Major Kururu
Kururu is the head of communications in the Keroro Platoon. Although he is of a higher rank than Keroro he is not the leader of the Platoon due to his unpleasant and unnerving demeanor which has given him the nickname of Yellow Devil. His blood type is AB which is befitting his Japanese blood type theory of personality . His name comes from the Japanese word for the phrase round and round kurukuru referring to the spirals seen on his glasses. Kururu a Sergeant Major in the Keron Army and the head of communications is the brain of the Keroro Platoon. He is mischievous deceitful and downright evil and enigmatic almost to the point where some people might call him a mad scientistcitation needed. He is generally disliked by everyone most of the characters seeing him as a depressing jerk and in the series action figures of him tend to sell very poorly on Keron much to Kururus chagrin but Kururu seems to take pride in his bad attitude. Despite this he gets along quite well with Mutsumi and Aki Hinata. Kururu and Giroro greatly loathe each other due to their vast differences Brain vs. Brawnand as a result Kururu usually uses Giroro as a guinea pig for any invention that he creates. Kururu in childhood used to be blue. Kururu has an affection for curry causing him to turn yellow.