A naturally airheaded but cheerful girl, Ui was the first one to encounter Kazuma when she accidentally got kissed by him when he tripped. Since then Ui has shown some romantic interest in Kazuma. Besides her dumb and cheerful personality, she is very fond of food (especially cheesed flavored "Umaibo") and always carries some snacks with her. She can eat portions that exceed the very limit of a human being without any trouble.