The manga took inspiration from the works of Edogawa Ranpo, most notably from The Fiend with Twenty Faces.
By day nine-year-old Akira Ijuyin 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 mothers, which Akira pulls off without any true objections or interactions.
One night Akira ducks into the room of five-year-old Utako Ōkawa in an attempt to hide from the police.
This as well as several other obstacles give the young couple's budding relationship a fair amount of difficulty.
Akira is so pure that he still believes in Santa Claus – this fact really surprises Nokoru and Suō.
When she meets Akira at the beginning of the story, she is heartbroken by her kindergarten teacher who refuses her love confession because of their 22 years difference in age.
However, she quickly finds herself attracted to the mysterious thief who just breaks into her room to hide from the police.
Although seemingly very rich, they have always coerced their husband – the original 20 Faces – and, later, their son Akira – to steal anything they like by claiming that they desperately need it.
Once they even attempt to help by arriving at the scene in disguise (as bunny girls); however, they only mess everything up and this results in angering Akira, though their sincere apology makes him unable to remain angry for very long.
As such, he's always at the center of every heist 20 Faces, commanding police officers despite the fact that he is in high school.
He will often show up at the crime scenes to give out half-hearted advice to Ryūsuke and the police, but for the most part cheers Akira on.