
Would love to see Fumi as uke although Shunpei as uke is super hot too. They're both should be reversible couple, it'd be HOT.

well... this is not a reversible couple because Fumi doesn't want to bottom... he is the one who refuses to change the roles, because he has explained that he doesn't enjoy that position

You go girl! Hahahaha

It's interesting, and the ending is a tragic full circle. The only consolation is all three of them are alive and together at the end of the story.
Kira (Ivan's experiment) , Grinja and Ashijan (the Company's experiment) whole life are an experiment. And after they went through so much unveiling the truth behind their existence, they ended up starting a new life together which is in truth another experiment (Dr. Go's experiment to revive/repopulate the barren Earth).
This will be long... the story took place in future Earth, post apocalypse.
The apocalypse itself caused by a disease/plague that killed women.
Fortunately human colonization on Mars and Moon are safe from the disease. Several companies from these colonization used the barren Earth to do a massive scale experimentation called Marginal project.
The Companies built human civilization on the barren Earth from scratch using clones/"children made in the labs" then used them as "lab rats". Of course the "lab rats" were kept oblivious, they think that the "Holy Mother" birthed all children.
The Companies then create the Center system to control/regulate the experiments.
Meanwhile a scientist, Ivan had an obsession to create a creature with omnipotent psychic power that basically can make anything it think of into reality.
Ivan succeed and the side effect: all four Kira are immune to the disease and fertile hermaphrodites (using their psychic power they can shape shift into woman).
After a turn of events Grinja, Kira, Ashijin meet each other and unveil the sinister truth about their existence/world/life and basically caused the second apocalypse, the flood. They survived the second apocalypse, but at the end of the story it's as if they go back to the initial point. Living their life together as test subjects of yet another experiment.
I'm a bit of a cynic so that's what I get from this manga, maybe others will have a more happier interpretation.

Not a fan of sea slugs but the story is cute. And hilarious (maybe unintentionally?) like the fishes milling about during sex scenes, a funny distraction for me or that sentence about the sperm turns into pearls hahah (≧∀≦).
I like the cheeky twist of oops I lied, you are not turning into human after all and then the merfolk turns out to have feelings for the magician (a twist from the disney story).
Loving all the willful queen ukes in the story. My favorite is the first story (the bully seme which actually failed at bullying because the uke got him whipped) and the fox story.