He is a kindhearted, yet sophisticated teenage boy. Kio is easily able to accept the proof that his new friend is an alien, and that both his other friends are secret agents. He knows how to handle firearms, though he is not sure what business his Uncle Yuichi is in to have them. He displays a strong sense of justice, and is willing to take action when he feels it is needed. This sense, and his treatment of others, draws the attention of his female friends. He is unsure about his reaction to all that interest, and their attention begins to cause complications for Kio. Eris the Catian in particular has decided that she wishes to be his mate as she is about to come into her first heat. In the final episode of the anime, he becomes a catboy.