The premiss of the story is very interesting. A world where angels have gone crazy and demons are actually more helpfull for mankind. So a group of fallen angels, or demons, have United to save humans from angels and the so called Venus. That said, the author clearly wanted a longer series to develop his ideas. I hope he could spark some interest and got the chance he wanted to make something bigger.
The art didn't impress me. The main characters are very ordinary. Specially Satan. That said, the angels are very cool. I also liked the idea the author had for the weapons. The clothes are also boring and bland. The scenery is almost non-existant.
The only development we get is for two characters. They get to know each other. It's the start of a friendship. The past of the main character is explained, but we can't really say that there was enough development to make them charming or interesting.
All in all, it is a cool concept, but for a oneshot on its own is just pointless. It's like having only the first chapter of a very long series like Naruto or Dragon Ball.
If you don't mind reading the first chapter of a long series that will never be completed, just go for it.