Darien Chiba is an older student who comes into contact with Serena at Crossroads Junior High. Though Serena is a poor student and a little on the ditzy side, Darien can tell that she is a good person. After a chance encounter, the two begin to form a friendship. Though he keeps a cool veneer, Darien has a crush on Serena – and the feeling is mutual. As a result of living alone with no family, Darien is often very quiet and reserved.

Darien is also the superhero Tuxedo Mask, who frequently ends up crossing paths with the Scouts, often helping them in their battles against the Negaverse. Darien's favorite attack is a rose that he hurls at the enemy. His destiny is to become Sailor Moon's husband and help her to save the universe and revive the Emperium.