Ultra Maniac OVA
High school student and girls' tennis club leader Ayu Tateishi bumps into transfer student Nina Sakura, who is crying apparently because she has lost something. Later on, Ayu finds a pink electronic device and gives it to Nina. As a reward for finding her item, Nina reveals to Ayu that she is a witch in training and she offers to cast her a spell to help her win in a tennis game against the boys' club. Unfortunately, the spell doesn't enhance Ayu's abilities; instead, it turns her into a boy.