The story deals with an amnesiac girl named Ai who was torn from her homeland, and awakens in present-day Tokyo. Remembering nothing of her life except her own name, the only clue she has to her identity is a heart-shaped box.
A young, amnesiac alien girl known only as Princess Ai is mysteriously transported to Tokyo, Japan. With only a heart-shaped box to clue her in on her past, Ai makes her living as a rock star at Club Cupid. She falls in love with a sensitive musician, Kent, to the chagrin of Kent's gay, possessive roommate, Hikaru. But Hikaru is the least of Ai's worries when gun-toting talent agents and demons seeking to take control of Ai's homeland, Ai Land, are hot on her trail.
- The main character of the story. Ai is the product of a relationship between her Human father, King Sei, and a [dead]Dougen (Angel) female. Because of the war that rages between the Humans and the Dougen in Ai-Land, Ai's true parentage was kept a secret, even from Ai herself. Due to her mixed heritage, Ai sprouted wings on her back and has the ability to control people's emotions with her singing.
- A young man who works at the Shinjuku University library part time. Kent was one of the first people to discover Ai after she appeared in Tokyo, and offered her a place to stay, an action which caused a lot of friction with his roommate Hikaru. Like Ai, he is of a mixed heritage, being half Japanese and half American, and uses this fact to help Ai come to grips with her dual heritage.
- Kent's gay roommate. Hikaru has a huge crush on Kent and a hatred for Ai fueled by jealousy. Later on in the series, he makes peace with Ai and becomes one of her biggest supporters.
- A street musician with strangely compelling lyrics who helps Ai discover her flair for singing. He has a knack for appearing and disappearing at just the right time. He watches out for Ai, and is associated with the fallen (Princess Ai : Prism of Mignight Dawn).
- A leader of the revolutionaries in Ai-Land, this Angel wants equality—not superiority—over Humans...but not everyone shares his views. He got really close to Ai and sent her to Earth for her safety .
- Nora's radical cousin who believes that the Human royal family must be conquered at all costs. Much to Nora's dismay, Kaz dispatched Tess to capture Ai. But later on , he discovers the truth about Ai and understands Nora's point .
- An angel, a witch, or a demon, depending on how you look at her, she's actually one of the Furies of Ai-Land sent to search out and drag Ai back to her planet. She later becomes Ai's body guard .
- The second Furie sister to be sent out to fetch Ai. She is devoted to Kaz and repelled by flowers.
- One of the Furie Sisters. She is Tess's sister, and Kaz's last hope to return Ai to Ai-land. It's suspected that she has a crush on Takeshi.
- One of the angels who helped with the second revolution, and is in league with Kaz. However, he now harbours a personal revenge against Ai, and is on the brink of insanity. (Princess Ai : Prism of Mignight Dawn)
- Tough, tattooed, and tawdry, he's a VIP at the nightclub Club Cupid who just happens to work for H.T.A., the hottest talent agency in Japan.
- Takeshi's boss, the powerful president of H.T.A., who's allegedly connected with the Yakuza (the Japanese mob).
- The one singer at Club Cupid who takes the time to befriend Ai. Later on in the story Jen dies getting Ai's necklace back from a robber.
- Ai's personal assistant. He is sometimes mistaken for a very tall woman.
- A rude woman at Club Cupid. Calls Ai trashy. Wants Takeshi to notice her own talent instead of Ai's.
Co-created by Courtney Love and D.J. Milky, Princess Ai was written and illustrated by Misaho Kujiradou and featured character designs by Ai Yazawa. Princess Ai was published in three volumes from July 6, 2004 to February 7, 2006. Tokyopop re-released the series in one volume, Princess Ai Ultimate Edition (ISBN 978-1-4278-0728-1), on October 9, 2007. Madman Entertainment released Princess Ai in New Zealand and Australia. The series is also licensed in Germany by Tokyopop Germany, in France by Soleil Manga, in Italy by J-Pop, in Finland by Punainen jättiläinen, and in Russia by Comix-art.
The sequel, Princess Ai: The Prism of Midnight Dawn, is currently being published by Tokyopop, who has released two volumes as of January 2010. It is also licensed in Germany by Tokyopop Germany, in France by Soleil Manga, and in Italy by J-Pop.