Using succubi as villains in a low-sexuality game

One of the players in my current group has a backstory that prominently features succubi as villains. I’d like to do something with that, but romance and sexuality are not a large part of the game. Per our Session Zero, these topics aren’t off the table, but the PCs aren’t generally motivated to sleep around, seek out romance, or do other things that would naturally bring them up. Two of the PCs are technically dating NPCs, but that mostly just means that occasionally we say things like:

GM (me): "Okay, you’ve killed the last troll and pocketed all the loot you could find. Where do you want to go next?"

Player 1: "We should probably return to town. We’ve got plenty of loot to sell and we haven’t been back in a few days."

Player 2: "Good point. When we get back, I’ll check in and see how [my girlfriend] Lily is doing."

Because this stuff isn’t a big part of the game, I’m not sure how to use succubi in an authentic way. A succubus’ primary ability is draining life with a kiss, but any flirty NPCs that I put in are likely to come off as suspicious from a metagame perspective. Now, I could just make this a background detail – e.g., some NPC is seduced and leads the PCs into a trap – but I want to explore my options first. Are there things that I can do to make a succubus’ life-draining kiss a threat in a way that won’t make the players immediately say, "this NPC who’s trying to kiss my PC must be a succubus or a vampire or something"?

(I’m mostly expecting Good Subjective answers, but I’m certainly open to other ideas.)