Very immature and shallow, there are no transitions what so ever in events and the author has as much understanding of human nature as a monkey. People start killing, betraying, stealing, raping, etc. etc. just a few hours after zombie apocalypse, sure, the MC has lived through it so his callousness is explained and there might be a few sociopaths in society but the rest, normal people just going wacko within hours is BS, people don't go from being a socially adapted person to live a "survival of the fittest" mindset in just hours, nor day or even weeks for that matter. He doesn't even bother to properly develop or portrait the secondary chars as proper humans, the MC went to save his sis, I'll asume he has no parents, but what of the rest? The other girls have no mind or will of their own, one is an idiot obsessed with chemistry when the world falls apart and people kill each other around her and the other is more busy falling for a guy that just goes around killing people as if it was completely normal, not one of all of them thought "hey I want to go check on my family" or "hey, I know they are not good guys but, is killing ok?" and so on... puppets. All girls are like that, by the way, 0for the inevitable harm, and they keep piling up, and there is only one other guy in the cast and he already wants to leave. The rest of the men were ALL rapists or treacherous bastards.
Same with the plot, a few hours later, not even 24hs after the fall and crystals are the new established currency... yeah sure, again, it takes time first for anyone other than the MC to even think of getting those, even more time for people to realize they have "cultivating" effects and even more time to be used as currency.
The author just childishly applies ideas and concepts without proper introduction or thinking how they would actually work in reality or bother if they make any sense at all. He just copied "The last Human" and "King of Apocalypse" without any further considerations, those two were already pretty messy and inconsistent and this one is even more so.