On his14th birthday, Daisuke Niwa tries to give a love letter to Risa Harada, but he backs down when she says she wants them to stay good friends. When he gets home, he learns that he turns into Phantom Thief Dark when he fondly thinks of Risa. Although he is reluctant, his grandfather and mother send him to his first mission to steal a statue titled “the Sacred Maiden”. On the way back from stealing the statue, Dark is spotted by Riku Harada and to keep her quiet he kisses her.
One night, under the eyes of police officers and journalists, two mysterious angels, Dark and his other self, Krad, battle until the latter is sealed into the Black Wings.
Two hooded figures, Daiki and Emiko Niwa, perform a mysterious ritual in their basement. Daisuke Niwa is also present, though he is uninterested in the ritual. As he rushes out the door to arrive at school early, he is warned by his mother to return home on time no matter what happens with his crush.
Daisuke, whose 14th birthday is today, carefully planned to confess to his classmate, Risa Harada.
Unfortunately, before he has the chance to give his love letter to the girl he loves, he hears her innocently tell him she doesn’t see him as a man, but as a friend.
Heartbroken, the teenager spends the rest of the painful day at school. As the afternoon is ending, wannabe journalist and Daisuke’s friend, Takeshi Saehara, tells him about a big event that will happen later and foists his cleaning duty onto Daisuke.
Daisuke later breaks into the art room by hacking the lock because he brought the wrong key card. At that moment, Satoshi Hiwatari, one of his classmates, appears behind him, claiming to share cleaning duties. His mysterious conversation about the important event happening that night unnerves Daisuke.
Upon returning home, he is greeted by a series of deadly traps which eventually lead to the living room, where his proud grandfather and mother wait for him. Ignoring their praise, he continues toward his room and looks at a painting of Risa that he painted. He remembers her rejection, which begins an uncomfortable transformation into an older boy.He runs back to the living room in a panic, where he’s welcomed by his enthusiastic relatives. Daiki tells him about his family’s fate: for 300 years, each male generation of the Niwa family inherited the famous phantom thief Dark once they reached 14 years of age. Daisuke is the next in line. According to Daiki, if he wants his body to go back to normal, he needs to obtain the Sacred Maiden. Misunderstanding that he needs to steal the artwork that bears the same name, Daisuke agrees to go to the museum using his pet rabbit, With, who can transform into Dark’s legendary wings.
At the museum, the police are gathered with Inspector Saehara who is confident and ready to catch Phantom Thief Dark. Emiko and Daiki, in the thief’s name, sent a warning letter announcing he would steal the St. Tears, the Sacred Maiden at 11pm. Takeshi is present as well to get his scoop, since it's been 40 years since Dark was last seen.
The arrival by air of Daisuke, in Dark’s body, is captured by the reporters, who stream it live on television. Risa Harada sees Dark’s face close up and becomes enamoured with him.In the museum, Dark cuts the lights which causes Saehara’s men to fall into chaos and leave the artwork unprotected. Satoshi, who is revealed to work for the police, arrives as Daisuke is almost finished stealing the sculpture and tackles him. Panicking, Daisuke hears a voice inside, and control of his body is seized by the real Dark.
After distracting and dragging Satoshi away with the help of With’s magic, Dark escapes with the stolen artwork.
While flying, Dark sees Risa and begins transforming back into Daisuke. He slowly lands on the balcony, where Riku Harada has replaced her twin sister in gazing at the sea. To stop her from revealing his location, he kisses her on the lips.
- The door to the Niwa living room has a round doorknob on the outside, but when Daisuke opens it from inside, he's pushing down a door handle.
- "You know me. I don't want to settle for someone who's just plain and ordinary. I want someone taller, who really stands out from a crowd. I've been working very hard, myself, to be suitable for someone who's just like that. So I feel bad for Niwa, but..." (Risa to Riku)
- "You don't know how happy I am you didn't get electrocuted!" (Emiko to Daisuke)