Although she is a middle schooler, Mitsu Kojima looks like she should still be in elementary school because of her small stature. As she attempts to put on a maid costume for a school event, she finds it difficult to fit into the oversized attire. While changing, she spots a tiny bat stuck in the window and chooses to help it. Without warning, a charming man appears from the darkness, disclosing that he is a vampire. As gratitude for freeing his "pet," he gives Mitsu a kiss that transforms her into an adult.
