D.Diver - Vol. 4 Ch. 36 - Blood to Entertain the Gods

[MangaDex]

 

[JohnSmithereens]

The cosmology of this manga is clearer now. Fiends = evil creatures/spirits. The Kagura spirit-god != true fiend, because it opposes evil, like it was mentioned in this chapter.
It is yet to be seen how the fiends (the two henchmen, their boss, and the whore) gained those powers. I think they are corrupt humans who were initiated by the bad guys boss. The boss can definitely bestow powers because the whore in this chapter was asking for those powers once again, meaning he had boosted her powers once before. Plus they all have this wavy mark on their body.
Also I wonder if this manga is made to be short, because they introduced the guys who killed his parents in this chapter and the bad guys' boss looks like he's the final villain, but we are only 36 chapters in.

 

[JohnSmithereens]

I predict that one of the themes will be whether the MC surrenders to the Kagura fiend. The bad guys surrender to their own dark desires and submit to the bad boss, gaining power but becoming twisted. Currently our MC is pondering whether he is using his powers for good and whether he is being controlled by the Kagura fiend -- which he clearly is, because he didn't know how to shoot fireballs, so the must've been the fiend controlling him.
If you enjoy these themes, I recommend Jagaaan. It has amazing character arcs dealing with these themes (heroism, lust, etc.)

 

[Kendama]

Also I wonder if this manga is made to be short, because they introduced the guys who killed his parents in this chapter and the bad guys' boss looks like he's the final villain, but we are only 36 chapters in.

Probably. Something like that has happened with this author before. When he was in the middle of a major serialisation, Suicide Island, he started Destroy and Revolution and finished it in 74 chapters. Now he's started D.Diver in the middle of Taiga of Genesis. So I'm guessing there's a pattern.

Another parallel between this and Destroy and Revolution is that while his longer series (Taiga, Island and his first, Holyland) all center around the trope of the "misfit young man looking for a place in the world", the shorter series depart somewhat from that theme. The protagonist of D.Diver is well-adjusted (or was, before the supernatural stuff started) and Destroy and Revolution had political and moral overtones, though it went to the dogs in the last third.

Perhaps these shorter series are how the author experiments with different themes and ideas. No surprise that I find them a little less intolerable than his main trade.