I read a story years ago about a mistress giving a man a choice to go into chastity with another (slave/lover) to compete and see who gets to keep her it had forced fem and coerced bi in the story
Maybe someone will recognize this, but there's virtually nothing there that I could search for and one of my frustrations with LE is that maledom and femdom are collapsed into the same categories (making these kinds of searches that much harder).
I wish I remembered more details
I can remember one scene where the femdom tied them up one at a time to release them as she watches from another room and the other lover tricked him into sucking him off with false promises of returning the favor when it was his turn to be unlocked and tied