Ace Kaitou
Alias:Saijou, Danburite, Adonis
U.S. Kodansha Name: Phantom Ace, Ace Saijyo

Making his first appearance after DeBrine's death to hand out Rainbow Candy (weight-loss candies) to all of her victims, Ace soon makes himself an Idol by appearing on TV in his own show, and by helping Sailor V (much like Tuxedo Mask).

His "Earth" name is Ace Saijou and he soon becomes Minako's top love interest.

His facade is that he wants to help all of the girls in the world, but in reality he's the main man behind the Dark Agency. In Vol. 16, Minako discovers that Ace is actually Danburite, and his story is the saddest of all...

During the Silver Millennium, Ace lived as Adonis, a foot soldier on the planet Venus, but was so low in rank that he could never meet his dream crush, Princess Venus. (Minako) Just like his dream woman, he too can make the sign of Venus appear on his forehead, and he lived not far from her castle, Magellan. He was sent to Earth, to serve under the 4 Generals. Here, he was finally able to see his princess up close, but by this time she was falling in love with Kunzite.

He muses that even back then, Minako was always falling in love.

Adonis would soon join Metallia's group, once he realized that the only true thing Princess Venus was ever married to, was her mission to protect the young Princess Serenity.

Once reborn, he was driven mad by his unrequited love, and was insistent on winning the love of Venus in this life. However he was already in charge of the Dark Agency as Danburite, and had to answer to Kunzite for each action of his minions.

Ace was gifted at fortune telling with regular playing cards, a talent he had retained from his past life on Venus. He also used the cards in all of his attacks.

While filming a movie in China with Minako, he revealed that he knew Minako's secret life as Sailor V.

He even teased her emotions by giving her a near-engagement ring in the shape of the Venus sign. But this was all just leading to his final act. Towards the end, he was locked in a fight with Sailor V on a movie set in China. But when a stone from Princess Lin-Lin's castle fell on her head, V began to remember her life during Silver Millennium. Her transformation as Sailor V melted away, and she became Sailor Venus.

Once Venus had learned of Ace's true form, he told her that he wished there could have been a chance for them to become lovers. But with that, he began to fight her, noting that in his new life, his duty is to kill her in the name of the Dark Kingdom. They traded attacks, until Venus accidently knocked Ace over a building's edge. She snatched his hand, begging him not to die, but Ace instead threw one more card, damning her to have all of her love end hopelessly, all of her days. In a twisted way, he also figured that by not focusing on love anymore, she could stay on her path as a Sailor Senshi, thus he viewed this as him doing her a favor. With that, Ace exploded, ripping himself apart in front of her.

His last resort however would prove to be a failure, as Minako later marries and has a daughter, Mina.

Ace is never mentioned in the anime, however in episode 176 in Sailormoon StarS, there is a scene where Minako daydreams about being in a play. A man in a white tuxedo appears on stage:

To The Secret Files of Codename Sailor V
To Moon Sisters