She is the daughter of Scarit. Scarit is a character in this cartoon that is presdnted in the second chapter, which is only in Japan. Scarit has now become the best friend of Keroro, but one day he was killed by Kiray, (Or even Kero.Exe). With his last strength he had left, he went by the protagonist and asked him to heal his daughter in his place, which was still very small. Keroro, who wept as he had never cried, he accepted the assignment. Then Scarit died, but happily. Sissy, his daughter, began to believe that Keroro he was shis father.