I read the scanlations, there's currently only 2 official volumes out as of writing this and there were none when I started reading. The scans can get pretty bad at times, so you've been warned.

As a hentai this would get a 10/10... but it's not a hentai, this is a manga. I think that ultimately tears me apart when trying to review this. There not the same standard, a hentai is suppose to explore sexuality and get you off and this manga does that better than most hentai. You could say Parallel Paradise is a paradox like that. Anyways, let's review.

Summery (Narrative):
Average teen boy get killed by a strange... thing... and is transported to another world. I'm this world there have been no males for 3,000 years. Women in this world look the same as our world but their bodies react wildy to sexual stimulus and even an otherwise innocent touch from a man can "flip their switch" into an extremely exaggerated heat. Thats the nice way to put it.
Note: the thing that kills, and the way it kills him,  is honestly terrifying. I get goosebumps just remembering it. Huge bonus points from me.
So this average chosen one must kill the generic witch of envy whos cursed womankind to die at age 20 if they haven't had sex. Our protagonist will be "saving" many of these women on his journey.

Discourse:
This all comes off as the opposite of what you might be expecting. Because our protagonist is a good dude, instead of subjecting these women to his will he is liberating them. He could have wrapped them all around his finger and created a monopoly on his d*ck but instead he gave these women the choice to save themselves and if anything this is a great exploration of empowerment. Yeah, it's such an exaggeration of real life that it almost has lost any meaning, but when you were 16 didn't it feel like you'd die if you didn't lose your virginity before you were 20? I think for most of us (regardless of gender) that's truly what it feels like. High praise from me, especially because it actively explores this throughout it's story.

Pacing:
Progression is fine, it's adequate, but most of you won't be reading for that anyways. In hentai terms, it's damn hot. Nobody is reading this for the plot, let's be real. It appeals to the what-if part of your imagination, it fills in a kink you might not of even known you had. Great stuff. At 150+ chapters already and no real end in sight this is the Boardline H version of a long running shounen, and when you think of it like that I think its doing a great job of fleshing out it's world and making you feel like it's making progress.

Art:
Art isn't suppose to "look good," it's supposed to make you feel something. I bought the first two volumes just to apply that phrase to this manga, and it holds up. I compared the first volume to chapter 120, and it does get better as you go on. The art compliments the dystopia/fantasy undertone to it. When it wants to look realistic it can, it allows you to feel dread, and all while still being destictive. One time I saw of panel of this manga out of context and I blushed, so that's pretty distinct. In that sense the art is great.

Overall (Enjoyment):
I know many of you are here because of the tags, your looking for something enjoyable to "research," thats why I picked this up, too. I'm here to say that you should read this, but only if you're ready to take on a new/invigorated watersports kink.