It was an AU where everyone was either a sub or a Dom. Kurt was a sub who had hardly ever left his house - being an unclaimed sub out on the streets was dangerous I think. Anyway, Blaine's parents and Kurt's parents knew each other somehow and the story happens the night Blaine is supposed to claim Kurt. They'd met once as children or something but were both pretty nervous regarding the whole thing. I remember Blaine asking Kurt to kneel in the living room, in front of their parents and there being a whole formal claim before he took Kurt to bed. The story is pretty much entirely smut and is sometimes from Kurt's pov and sometimes Blaine's.
Additional info if it helps:
Pretty sure there's a sequel
Blaine went to get fruit at some point in the night for Kurt
Traditional for the sub to move in with his/her Dom after this one night
Kurt was worried Blaine would disregard everything Burt had put into this night because he was used to wealth
idk if there's anything else I should write I think if anyone knows the story it should be clear by now so please help!