
I may be wrong but Chapter 4 page 20: His shirt say Rukawa Iichi... and the way he posed... it led me to believe that this might be a reference to Slam Dunk's Rukawa, number one player?
http://www.mangago.zone/read-manga/go_houbi_chikubi/nmt/d0563e20cc89d7bdb2d67ad4d7040ee1_chapter-4/pg-20/

and I see some... let's just say... "rude" comments (because I'm thinking of a much bad word right now)...
Most humans can't be content. And what those people did to the uploader... sigh... (I'm thinking positively and the ones who messaged the uploader were actually homophobes who wanted the story to stop being updated.)

That was anti-climactic... Oh well, since this is an open-ended story, I'll give my own theories. Mugetsu became the 'god' of the world after she killed Aco Atmos. It's been so long but I kinda remember that Aco Atmos said to junpei that he was previously a human who gained too much power and became a god(as I understood it).
As for Junpei... well... maybe they actually went back to their original world and the reason why he could still see the skill window is because he was a transported human? Like, "now that you're aware of it, you can't unsee it." Kind of thing. Almost all transported people are from earth after all, Junpei's classmates, Mugetsu looks from earth, and I bet that Aco Atmos is also from earth. OR They didn't went back, they are in the same world that Mugetsu now rules which looks like japan. Different god, different world kind of thing.
Things gets wonky when beings mess with time and space.

I don't think I'll be as inactive as Rimuru... I'd start plotting to completly destroy the ones responsible. Complete and utter decimation.

Fufufu you’re not entirely far off with the nuclear thing, though it’s tad different from a mushroom explosion... but just wait it’s gonna be soo awesome ! I’ll give you a little hint if you like ...
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Not a single soul will be spared fufufu ლ(´ڡ`ლ)

It’s so awesome ! It’s chapter 69 and chapter 70! ヾ(☆▽☆) and this arc is also where my favourite of his subordinates finally makes his entrance ! ε=ε=(ノ≧∇≦)ノ

Honestly ! This arc is so awesome ! ヾ(☆▽☆) Two of my favourite characters finally shows up ! ε=ε=(ノ≧∇≦)ノ

Damn dudes!!! A Bull and a Wolf fighting for a twink... and said twink has a muscle and furry kink... Hahahahaha seriously, this is some lowkey gay xD hahahahaha (Notice that hibiki isn't exactly interested on women's and such though he appreciate their beauty? But when he saw some muscles... his switch turned on. xD) hhahahahaha
This is so realistic in a way that... Gays daydreaming that their staright crush would go gay for them... Unrealistic though since it's just a dream, unless that "straight" is actually either Bi or a closet case (even then, there's a possibility that they might not like you since you're not their type. xD)
This type of stories makes me laugh sometimes... coz it's just sad... xD
So true, lol.
At least thankgod that no "straight" person in these mangas is actually straight. But they do kinda shitty teaching, so that then real people, possibly gay/bi don't really understand the meaning of straight or bi, keep on mixing them xD It's sad actually :(