Complex sentence: Sea of Darkness marks the first entry in the "Nancy Drew" adventure series that a character is revealed to be gay, as the character Dagny is described as breaking up with her life partner Alicia before the events of the game.
Split into simpler sentences: Sea of Darkness marks the first entry in the "Nancy Drew" adventure series in which a character is revealed to be gay. The character Dagny is described as breaking up with her life partner Alicia before the events of the game.