Sans- Lol really? Come on, as if he'd even care about that stuff. Like sure he could do it if you wanted to but if you didn't wanna then why should he go and do something with all that? He's happy to just cuddle you... silly person. Yeah, he doesn't care that you're asexual, he doesn't really even wanna do that stuff. It's too much to do and he gets tired often so... yeah. Have fun just cuddling.

Papyrus- What? Why would he leave you over something as silly as that? He doesn't need to have... that to be happy! He got with you because he wanted to cuddle and kiss and do things like that not... other things! Plus he isn't really even sure how that would work between a human and a skeleton? If they ever want to have a kid, he'll just borrow your soul for a little bit and take some of your magic then add his own and boom! You two have a child! Isn't that fun? Honestly just the thought of the great Papyrus leaving you because you're asexual. Gasp! Can't believe you'd say that.

Blueberry- What does asexual mean? Well when you told him what it meant he'd be like ohhhhh.... okay! Cool why should he care? Oh no wait okay it isn't that he doesn't care, it just doesn't bother him! The idea of... sex isn't really something that he needs in a relationship plus he isn't sure how that would work for monsters and a human. He thinks it's a little funny you were worried about it, you know that Blueberry loves you you're his datemate! He'd never leave you over something as silly as you not wanting to have sex.

Stretch- Funnily enough, I picture Stretch as asexual himself! He doesn't really see why he should want to do that sorta stuff, it's a lot to deal with and if he wants kids he could just like adopt or something? Or just mix their magics together... so when you told him he would smile and say "Saaammmmmeeeee" all while laying like upside down on the couch. What a little dork.

Red- To be honest, he is a little bit disappointed. He wonders if that means you don't want to date him? When you explained that no, you just don't do sex and stuff like that, he would be confused but doesn't really mind! It's all a little strange to him and he doesn't understand but hey, you're allowed to do whatever you want? Why should he care? He can deal with his own things if you don't want to do that 'dance' with him then fine it's okay.