I forgot the name

There's this incubus who is the uncle/friend of the Mc and Mc is a knight who likes the other knight ( he's blond) the incubus manipulates the ml thinking he was fking the Mc and in the end they had a threesome because the incubus said to meet him at his room ( telling the ml what to do looking like mc) ML doubt what the Mc ( incubus in his dreams ) said but is curious on why he said it so he went there at the same time and location to what the Mc ( incubus) said to him, then he witnessed Mc getting banged by an incubus, but the incubus signaled the ML to keep quiet and join, that's why they had the threesome