Meimi Haneoka is the main protagonist of the series. She is a cheerful orange-haired fourteen-year-old student at St. Paulia's Private School, with some minor attributes of a tsundere when she bickers with Daiki. At school, her strong point is physical education, but she is rather poor at math. By night she transforms into Phantom Thief Saint Tail, who has a long ponytail for her hairstyle, and is usually dressed in purple-black. In this guise, she takes back what bad people have stolen. Unlike magical girls, Saint Tail does not have actual magic powers; instead, she uses stage magic and theatrics, along with acrobatics to fool and confuse pursuers. She is given information by her classmate, and nun-in-training, [|Seira], of misdeeds. Her catch phrase is: "It's showtime!" Saint Tail is persistently pursued by Asuka Jr - by his request, she sends him notices of her crimes in advance, so he may have a fighting chance. As Saint Tail, Meimi consistently outwits Asuka Jr. in her capers, and as she observes his exclusive devotion to pursuing her, she begins to fall in love with him. As Meimi Haneoka, she usually ends up arguing with Asuka Jr as all he cares about is catching Saint Tail. As a result, Meimi constantly gets jealous of her alter ego. In episode 26 of the anime, Ryutaro Tomikoji proposes to Meimi, but later on falls for Saint Tail instead. In the final episode, Asuka Jr. discovers Saint Tail's true identity, but still keeps his romantic feelings for Meimi intact regardless. Meimi gives up her identity as Saint Tail in the process, claiming that Saint Tail 'has been put behind bars'. In the epilogue, which is set 8 years later, Daiki proposes to Meimi with an engagement ring, which she gratefully accepts. Meimi has also cut her hair short; now similar to that of Rina's hair length.
Daiki Asuka
Daiki Asuka is a detective boy fourteen-year-old at St. Paulia's Private School, and is a top student in his class. He lacks physical strength and motor skills. Commonly known as Asuka Jr., Daiki Asuka is the son of Detective Tomoki Asuka. Because Tomoki has been unable to catch Kaitou Lucifer, and also the fact that he is evidently apathetic of Saint Tail's crimes, Asuka Jr. takes up the mantle on capturing Saint Tail instead. Asuka Jr. is awarded a badge from the mayor, after he manages to snap a photo of Saint Tail. The badge grants Asuka Jr. the authority to investigate anywhere he pleases, and as such he is now able to assist the police in Saint Tail's capture. At his own request, Asuka Jr. is given prior notice of Saint Tail's crimes. As Saint Tail slips away from Asuka Jr. caper after caper, she becomes the object of Asuka Jr.'s thoughts. Very dense regarding relationships, Asuka Jr. fails to see Meimi's growing feelings for him. He often argues with Meimi over Saint Tail and his inability to catch her. Asuka Jr. begins to think of Meimi when he sees Saint Tail, and vice versa, and is torn between which of the two he's falling in love with. Despite that, he confesses to Meimi that he loves her in episode 40, with Meimi reciprocating his feelings. Only in the last episode of the anime does he know that Meimi is Saint Tail. Contrary to Meimi's constant fear of Daiki would hate her if he ever found out her true identity, she was proven wrong when Asuka Jr holds her tight and affectionately in the final episode after falling through the ceiling. Daiki states that he has caught Saint Tail and that she will be "put behind bars" so there's no reason for Meimi to be Saint Tail anymore. 8 years later, in the epilogue, Asuka Jr proposes to Meimi, in which she happily accepts.
Seira Mimori
Seira Mimori is a quiet and mature, thirteen-year-old student at St. Paulia's Private School and a nun-in training at the school's church. Classmate and best friend of Meimi Haneoka, she is the only person who knows the real identity of Saint Tail. After school, Seira spends her time at the chapel as a nun; there are many people who come to her and talk about their problems, usually involving something being stolen or going missing. She relays this information to Meimi/Saint Tail, asking her to help these people recover their valued possessions. She was the first one to realize Meimi's love for Asuka Jr. In some instances she also advised Meimi to give up being Saint Tail, so as to not hurt Asuka Jr. if he finds out. In the epilogue, Seira is shown to have become a professional nun.
Supporting characters
Haneoka family
St. Paulia students
; and ;Yasuhiro and Chiba
Other characters
;Detective Asuka ;Mayor Hideo Morinaka ;Rosemary/Kabako Sendo ;Maju Sendo
