Which is a little synonymous with mature seinen.
Have you read any manga with sex galore that still has an amazing plot?

I personally can't think of any that really pops out to me...

But Tokyo Red Hood made some attempt at a plot...

And Bradherley No Basha wasn't bad either.

Berserk had a hentai-esque rape scene in the middle [but who agrees that Berserk's just been going down?].

Oooh and Tropical Citron was amazing.

I wonder if it would be even rarer to have light-hearted hentai/mature manga with a plot. Chances are anything like that just ends up with a manwhore like Virgin na Kankei. 😛

Edit

To add some more to the list that I felt had some sort of plot:

Alice in Sexland
Some of Yui Toshiki's work.
Ne.to.ge
Petit Roid 3
Slut Girl
Dulce Report

I admit, some of these are really half-assed attempts.
And do correct me if I'm wrong, I haven't read some of these in a while.

I know some, but the only one I can name off the top of my head is Witchcraft.

Or if you don't want hentai, Love Junkies is pretty good.

Quote from Klapzi

The cool part is that I never get tired of being deceived

Quote from tactics

Just because someone's head was chopped off doesn't mean they're dead. That's just silly.

[img]http://oi44.tinypic.com/vzy2qv.jpg[/img]

Hey there's the newly "revived" RingxMama, very funny XD

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I need a die with 2 sides.

That's known as a "coin".

Oh, thanks. Too much D&D.

Love lucky, Haru yo, koi not H but pretty dam close n///n I suggest u search in
http://www.mangaupdates.com/series.html?category=Borderline+H
or
http://www.mangaupdates.com/series.html?genre=Hentai_Romance

also hatsu inu and Ojousama to Boku

Reading Love LuckyRecommended B Gata H Kei <3 Conveni-N XD

I'd say try reading Hatsu Inu and Hana Fuda.

If you like Hatsu Inu, don't touch the h-anime.

oh and of course, a classic: Slut Girl 🙂

Quote from Mamsmilk

Quote from x0mbiec0rp

Quote from Mamsmilk

I need a die with 2 sides.

That's known as a "coin".

Oh, thanks. Too much D&D.

Thanks for the replies~~

I've read a few of the suggestions before, and the only one I would consider has a plot would be Hana Fuda, for a few reasons.
(Correct me if I'm wrong, it's been a while since I've read Hana Fuda)

Hatsu Inu and Witchcraft are hilarious and amazing hentai, but as far as a plot goes, it's only a common motif linking the chapters, unlike other hentai which are oneshots. [Don't get me wrong, by all means continue reccomending hentai like Witchcraft 😀 ]

As for borderline-H, I actually don't like ecchi. It's strange, but as a female I find ecchi repulsive and hentai absolutely acceptable.

I'll read the other series, and keep on reccing, please ^_^

edit I guess I'm too picky. If there's a plot, there's a plot 😛

I myself didn't like these, but Love Comedy Style and Itoshi no Kana might fit.

Hrodulf and Bjornolfr, you will not be forgotten.
[img]http://i411.photobucket.com/albums/pp199/SyberAngelGabrielle/couplesig.jpg[/img]
[color=black]And if the world were black and white,
you would be my rainbow in shades of grey.[/color]

Click 'n Play!

If I had a fantasy self, it'd be a tentacle monster.

How has Take on Me not been mentioned yet.
Dulce Report by Behind Moon who more or less specializes in futanari
Sei So Tsui Dan Sha
sexcapades
Were-Slut
♭37°C
Prince of the Stars
Secret Plot and Secret Plot Deep
Sex Phileswell, its more an anthology of stories and some are better than others

Oh! great also did some pretty good stories way back. Normally, OH! great and good stories don't normally go together, but his h-stuff was really good.

Sarcasm just doesn't work over the internet.

I'll add Ah! My Goddess dj - Nightmare of My Goddess to the brawl XD

Quote from Mamsmilk

Quote from x0mbiec0rp

Quote from Mamsmilk

I need a die with 2 sides.

That's known as a "coin".

Oh, thanks. Too much D&D.

Great Recommendations!~~~ Some of which I'm already familiar with.

Any more are welcome ^_^

*To be picky, maybe something that justifies itself... acceptably? 😛

nana to kaoru borders on hentai and is pretty strong when it comes to story