Kuroinu: Kedakaki Seijo wa Hakudaku ni Somaru

in both u can see princesses and queens being boned by human as well as monsters don't worry(no tentacles) i liked the concept of Kuroinu i wish there was a place where men can bone any women they want Animation quality of Kuroinu is great too 

Royal women are gang raped, humiliated and transformed into sex toys by a perverse group of foreign invanders. 

Monster ogre sex (with very big dick), with ahegao expressions on women. Abuse and rape. Don't watch these if you can't tolerate this "acquired heavier taste" in hentai. 

Similar plot of princesses being seduced 

Both Kuroinu and Sukebe Elf are hentai involving elves and dark elves in a fantasy setting, if you're interested in that you may like both, but just bear in mind Kuroinu is not vanilla like Youkoso! There's rape, gangbang and the like. 

Similar plot consisting of ogres, monsters, etc 

3Ping Lovers! Doesn't have the fantasy tag in the genres, big error, since it's a fantasy hentai through and through, RPG references, the protagonist getting isekai'd, dark and normal elves, ladies with skimpy armour, everything points to the direction of fantasy, and so does Kuroinu, many elements are the same fantasy style, like the elves or the female knights, the main difference though is that Kuroinu is not an isekai and it's not vanilla, there's actually lots of hardcore stuff, but at the end if you like the mix of fantasy with hentai, then they're both recommended. 

Similar fantasy theme 

In both the MC tries to conquer the kingdom by forcing girls to have sex with him, there are also extremely hot elf girls and the high elf is the leader in the kingdom. 

Girls getting banged by monsters. And that huge amount of cum. Both are definitely good fapping material for super degenerate people. 

Both female main character are caught and "attacked" by monsters, orcs, aliens, etc. 

Rape is one of the main plot points in both series. Though it's not the main focus for the Toshi Densetsu Series. But I'm certain that if you love Kedakaki Seijo wa Hakudaku ni Somaru, you'll love Toshi Densetsu.  

These two hentai have similar plots where a female prisoners must have sex at the beck of their captors. 

Love lolis? Let us pinpoint something specific here, Kuroinu episode 3's lovely Ruu Ruu and Inyouchuu Shoku's adorable Tsukishiro twins from the bonus episode. YES! lolis getting stuffed to the brim here. The smaller they are, the bigger the dicks will be! Massive penetrations, some of the craziest stomach bulging you'll ever see, copious amounts of cum inflations, ahegao, yeah it doesn't get much more epic than these scenes. 

Similar (hentai) fantasy setting, with knights, princesses, and loads of monsters. Watch with caution. There are a lot of hardcore scenes. Also, both hentai anime have a fetish for virgin princesses. 

Have in consideration that while Kyonjuu Fantasy is more a harem vanilla, Kuroinu is pretty hardcore in term of kinks, rape, deformation, bug, gangbang, masochism are some of the sub-genres that has , with that said it's not like I don't recommend it, both are fantasy oriented hentai with great art and animation since it's made by the same studio of animation, it's just something you should have in mind if it's the one you've yet to watch.