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Okay listen I need horny twitter to understand something. A succubus is a bottom and an incubus is a top. In theory they should have the cishet-y parts associated with each, but a succubus specifically takes semen and then transforms into an incubus to ejaculate it back out
These concepts developed in a time when women were accused of sleeping around because they had weird deformed babies and/or babies that were clearly Some Other Dude's Kid TM. The idea was that succubus would seduce a target (human or otherwise) for its semen, then wreak havoc -
By transforming into an incubus and inseminating some poor woman with goat DNA or what the hell ever. It probably saved a lot of women's asses, but it also was a huge part of how people were persecuted during the witch craze of the 15th-17th centuries.
ALL THAT BEING SAID, if your gay otp is two dudes and the incubus is getting it up the ass I think you should just go the extra mile and call him a succubus because gender is fake but historic demonology is real 
