Forbidden love with a spy/assassin fmc and mmc who's her handler or just her superior

A bit specific lol but I've been watching rewatching Nikita and a bit obsessed with the whole dynamics going on there.

I want a thriller subplot but it's not really needed. What I really want is a true forbidden love like falling in love could get them killed. Also better if she was forced into doing the spy/assassin work and dislikes the MMC because of that. Maybe the mmc could be cold and detached and deny any feelings towards her.

No instalust please. Also I wouldn't mind age gap