The world the MC is transferred to is a fantasy empire in which females are the strong, the powerful, and the rulers. Men are considered to be little more than tools, cattle and, especially in the Valhalla brothel, merely there for the female's s*xual release. Men, on the other hand, are weak and delicate. They are cowed by the females and are hurt psychologically by their violent need for s*x.

In other words, men are the "fairer s*x" here.

Enter the main character, a pe*verted young modern Japanese man with a thing for foreign women. In addition, his assets are peerless in this world. Unlike other men, he is excited to entertain the desires and needs of the women. He willingly takes the place of men who are being oppressed by their tyranny. He has the ability to satisfy these voracious women in ways they haven't ever experienced before. He does so happily.

Oh, and there is a dragon/demon girl we just barely met.

the mother succubus part seems a little forced, after that it smooths out, author just seems to mostly want to include alot of races in this s*x novel, theres a few arcs that arent done well and u can tell when the author took off for pubs or blocks when writing, only failure from a wn reading perspective is the too long but wanted to include alot of elves/spirits s*x plots that took way too long to incorporate for one of the main mc's as a back story/explaintion overall, if that was shorted by half then we could see more timeline/plot advance, not sure if its due to pubs and manga or writer blockage,

We have a short (shota) japanese High Schooler, who mastrubates 1000 times to his favorite illustrated fantasy erot*c novel. Where it happens, his seed hits the book cover, a light emits and the next thing he sees, he is stark naked in a prison with other boys. What he doesn´t know he was transported in a s*ave prison from a fantasy world, where woman only use men for stress relieve or producing children. As a man with the biggest p**is in this world, he will rise his position as a male prostitute.