The story of 20 Mensou ni Onegai!! centers on Ijuuin Akira, a nine-year-old boy who steals exquisite and valuable items to satisfy his two mothers. The general public knows him as the skilled and charming burglar named the Man of 20 Faces. During the day, Akira attends classes at the Clamp School like any ordinary student, but when nighttime falls, he transforms into the elusive and enigmatic 20 Masks.
Akira's criminal exploits are often at the behest of his stepmothers, and he executes them without hesitation. However, a chance encounter with a five-year-old girl called Ookawa Utako changes his life forever. While on the run from the authorities, Akira takes refuge in Utako's room and discovers a newfound romantic connection with her despite their significant age difference. Their relationship is tested when Akira becomes increasingly involved in more audacious thefts, some of which even affect Utako's family. The hurdles they face put a strain on their burgeoning love affair, adding more layers of complication to an already complex story.