Ooh, I love this! Ever since the first part of Patema came out, I've been fascinated by their world - I'm stoked to get to see more of it!! ^^
As for the artstyle, lots of published manga actually looks like this. I think I've read several in the postapocalyptic and shôjo-ai genres, anyway, no doubt there's lots more. I actually enjoy the sketchiness of it, it lends itself well to the cluttered nature of the tunnels.
I hope to read more soon~ :)