For Blaine, there are no feelings involved, at least in the beginning. Kurt thinks there's more to them than sex but then hears that Blaine sleeps with other boys too (I don't know if he really does or if it's just a rumour)
There's a scene where Kurt confesses to his father about it and says that he wasn't ready. He breaks it off with Blaine.
The story follows canon roughly.
It's kinda angsty but with an happy ending. It was a longer story and probably not on AO3 (but I'm not 100% sure)
Eta: Found, link in the comments.