love interest 
noun
1An actor whose main role in a story or film is that of a lover of the central character.The role of the female love interest in Arthur was similar in style....
- As the central love interest, he isn't charming, just irritating.
- The character of Nikki, the love interest in the novel, is particularly strong, and is again based on old colleagues.
1.1 [mass noun] A theme or subsidiary plot in a story or film in which the main element is the affection of lovers.And while the St George story was lacking in any love interest, the theme of life and rebirth is a common one at the festive season....
- This is unfortunate, given they're the film's main love interest.
- There is none of our modern screenwriting need to provide story arcs, lenient human touches and love interest.