We all have our fetishes and tastes. But occasionally, something outside that box will hit the mark. Either it turns you on despite being in a genre you hate, or provoked thought instead of or in addition to playing with you naughty bits.
And for this... let's just set Metamorphosis to one side for now
There's a story by Takenoko Seijin. You Are Just A Maid. I'd already read some bitter endings from this mangaka, but this... this showed how being in a position of power over someone you might come to care for can be really bad juju. Like many of the best 'hurts' stories I've read, I found myself seeing all the ways it could have turned out different.. but also knowing why it didn't.
Poni Parade, Ok it's mostly a western work, but it has artists from Japan.
I tend to loathe bronies, but I have to admit that book has some good stuff.
I was never a fan of puke until Meme50 released Lets Puke! Cure Sunny Vomits. It's still out of my comfort zone but thanks to him repeatedly adding a vomit scene in his doujins, I'm starting to like it. If only all the other artists could draw it as un-gross-ly as he does.
I tend to avoid NTR as much as possible, but I found one called Ai no Neuchi by Kizuki Rei that I liked. It's this weird story where couples are formed based on matching scores, like an SAT test...only more interesting. Basically the main girl ends up ditching her boyfriend for a fat slob who got the same scores as she did. She just runs to him and they start fucking right in front her boyfriend. I nearly pissed myself I was laughing so hard. lol