...which is to say that aside from the Easter eggs, this whole thing is going pretty downhill like Cage of Eden did with its rushed ending, only in this case with Deathtopia, the whole thing picks up CoE's decline right from the very start.
For the sake of some additional context:
At a certain point the whole story in CoE became really rushed in which nearly every chapter basically ended up being a ridiculous cliffhanger posing the usual questions (How will our heroes ever get outta this sticky situation?), only for it to kept pulling twists out of its ass as nearly every potential conflict was either solvable to result in almost no casualties, or just wasn't a real danger at all. Back in late 2012 to early 2013, translated chapters were being thrown at us weekly, till it was surprisingly declared as "completed." People were really in shock, as the ending still left various questions unanswered, and even left it highly opened for a follow-up sequel that could've played out like Green Worldz, I Am a Hero, Gakkou Gurashi!, etc., as perhaps the island turned parts (or even all) of Japan into apocalyptic urban wastelands, where the original + new/mutated flora and fauna from the island repopulate and spread throughout the land. This was just a potential idea I had in mind at the time when envisioning a possible sequel, but all-in-all there's no way of saying that that would be the actual case if it would ever come to be...
Speaking of which, it's highly unlikely that there'll ever be a sequel due to the the author currently working on Deathtopia, and believe me, I'd love to be proven wrong on this. For what lays before us now though, we have a series that's set up with the usual premise: "Your typical young male MC that's living an ordinary life, until a supposedly tragic car/truck accident occurs. This ends up changing his life forever once he unlocks some amazing hidden power(s), and on top of that, he ends up becoming acquainted with some (I'll admit it's usually just one, which happens to be the heroine in most cases...) beautiful girls that fight alongside him in the never-ending battle between good and evil."
So yeah, it's that kind of story, except it's playing out with a lotta grit. Looking back into it once more while I write this, I'll admit that the author does a pretty good job when it comes to drawing human bodies, mainly being those of sexy women or those of freshly made corpses (at least check out page 41(?) of Chapter 16 to see what I mean by this). His style was distinct enough to have me immediately recognize him as the author of CoE, and like I said, he knows what he's doing in this department.
That said, I have barely any clue as for what's going on with him and the story department. The story itself is extremely lackluster, and never really jumps out as for introducing, exploring and expanding upon some cool potential concepts. It sums up as "the MC can literally see with his own eyes who exactly's a deranged murderer hiding amongst society, as the supporting girls use their weapon expertise to try and take down these abnormally strong baddies."
The girls themselves are alright, but because they're all beautiful girls and he's just an ordinary guy, fan service cliches are thrown into the mix, and I hate how the whole thing's being handled. The manga's tagged as harem, yet so far none of the girls hold feelings for him, so it seems romance nor even some decent comedy will be around to give it something to work off of. And like bobIV123 said, the grit and ecchi do not mix well in the grand scheme of things.
I think it can maybe, just maybe become something good in the future, but for now it doesn't quite hold up on it's own as a pretty interesting manga to check out, especially when there's the large CoE shadow constantly hanging over it. Perhaps try out Keyman - The Hand of Judgement if you're looking for a much more absurd approach to the whole gritty, action-packed mystery thriller with a little ecchi sprinkled into the mix, but all done very well and quite creatively.