20 Mensou ni Onegai!!

20 Mensou ni Onegai!! is a about a nine-year-old boy named Ijuuin Akira who steals beautiful and valuable objects to please his two mothers and is known to the public as the dashing, clever thief named the Man of 20 Faces.

By day Ijuuin Akira is a normal student at Clamp School, but at night he becomes the mysterious thief 20 Masks. His thefts are usually subject to the whims of his two stepmothers, which Akira pulls off without any true objections or interactions. One night Akira ducks into the room of 5-year-old Ookawa Utako in an attempt to hide from the police. Although the pair shares a four-year age difference, they find themselves quickly falling for each other even as Akira finds himself being increasingly more involved with thefts, some of which include Utako's family. This as well as several other obstacles give the young couple's budding relationship a fair amount of difficulty.

(Source: Wikipedia)

20 Mensou ni Onegai!! occurs simultaneously with both Clamp Gakuen Tanteidan and Gakuen Tokukei Duklyon. This is demonstrated by a conversation between Nokoru and Suou in Clamp Gakuen Tanteidan; while in Gakuen Tokukei Duklyon, Akira and Utako appear at their age as they do in 20 Mensou ni Onegai!!. The manga took inspiration from the works of Edogawa Rampo, most notably from Kaijin Nijuu Mensou.

The manga was published in English by Tokyopop on May 6, 2003, and Jul 15, 2003, and digitally by VIZ Media under the VIZ Select imprint from December 15, 2015, to December 29, 2015. It was also released in Brazilian Portuguese by NewPOP Editora from September 2013 to November 2013.