This particular WN is the first I've read that isn't another world fantasy or isekai.  

The first thing I found myself comparing this to was Devils Devel Concept.  Why?  There are a lot of reasons, but a lot of it is that the protagonist is a monster in human skin and most of the characters remind me of the characters from that VN.  

The setting is based six hundred years after the near-destruction of civilization earth due to a massive war (basically WWIII), and humans have the option of using the Oracle system to find their perfect job.  When Ibuki, the protagonist, activates the Oracle terminal, the perfect job for him is 'Daiyoukai' (great youkai), and he immediately is given an all-expenses paid trip to the mystic world that lies on the other side of reality.

One thing I have to note is that Ibuki is not a person who works hard or trains or any of that stuff.  In his own words 'A great youkai is something you either are or you aren't.  You can't work hard at becoming one.' He embodies his own words from beginning to end, easily awakening to his power because his unique psychological structure is perfectly suited for it.  The heroine of the story (there is only one) is Tamamo no Mae/Daki, who is also his ancestor.  She is pretty horrible as a person, manipulating those around her with every word, gesture, and even her rhythm of breathing.  Ibuki, even as he lives with her, constantly comments that she is a 'dokufu' (poison pill of a woman), but this doesn't really effect how he feels about her, which just goes to show how much a monster he is as well.

I honestly loved this story (it is over), and Ibuki was an ideal protagonist from beginning to end.  However, he is definitely a chaotic evil character who sometimes wavers into chaotic neutral.  As he notes 'Daiyoukai, by their very nature, are poisonous to humans, as they contain a certain evil from the moment they come into being'.  Ibuki, while he is often good to those he likes, is just as often a horrible influence that subtly - often without intention on his part - corrupts those around him.  

Definitely a fun ride, at least for me.

https://ncode.syosetu.com/n2559fp/