Tuxedo Mask is the alter ego of Darien Chiba (english name ) Mamoru Chiba (japenese name) in the anime/manga, Sailor Moon, and the romantic love interest of Usagi Tsukino(Sailor Moon), and later sweetheart, lover, and boyfriend of the main character.
History1000 years before the series began, Darien was Endymion, the Prince of Earth who fell in love with the Princess of the Moon, Princess Serenity. This love drove Queen Beryl into sadness, because she herself was romantically in love with Darien as well. This lead to her to release Queen Metallia and all of the Dark Kingdom and the entire Moon Kingdom was destroyed.
Queen Serenity, Princess Serenity's mother, used her powers to seal Queen Metallia away, along with the Dark Kingdom and sacrificed her own life to send the people of the Moon to the future on Earth, including Darien.
After reincarnating in the 20th centruy, Darien was orphaned at a young age. His memories are wiped and replaced with visions of his former life, leading him to search for the Moon Princess. At some unknown point in time he took on the disguise of Tuxedo Mask. Tuxedo Mask would appear whenever the Sailor Scouts were in a tight spot, either saving their lives giving them emotional strength. Over time Tuxedo Mask regained his memories of his life as Endymion.
Darien is generally shown to be serious and distant, but also incredibly kind. The only person who can stir him up is Usagi.
As Sailor Moon and Tuxedo Mask they have a flirtatious relationship but never get close enough to learn each
other's identities. Once they regain their memories, they become a romantic couple, though they temporarily broke up after Mamoru keeps getting nightmares of a horrible fate befalling Usagi if they stayed together.
Mamoru is 4-6 years older than Serena. By the end of the series the two are happily married and will eventually
have a child that would become Rini/Chibiusa.
While Serena and Darien were fighting, Ray Hino/Sailor Mars tried persuing Darien. The two dated briefly, but there clearly wasn't any chemistry between them. After Darien is revealed to be Tuxedo Mask, Rei steps down and allows Usagi to be with him.
Queen Beryl fell in love with Prince Endymion long ago. Upon finding out that he loved the Moon Princess, Beryl went mad with jealousy and dedicated her life to destroying the Moon Kingdom. In the present, Queen Beryl manages to brainwash Tuxedo Mask into being her servant and presumably lover. After Sailor Moon broke the spell, Mamoru turned on Beryl and managed to injure her before she was beaten for good by the Sailor Senshi.
Chibiusa is Mamoru and Usagi's daughter from the future. She doesn't make the connection between them and her parents and thus has no qualms about flirting with Mamoru. Usagi senses some closeness between them that she thinks is Mamoru replacing her with someone else, but soon realises that this is just Mamoru's paternal instinct.
- In his street clothes, Mamoru tends to wear black sunglasses, contrasting his appearance as Tuxedo Mask.