My review, taken from Myanimelist:
After reading Onani Master I learned to not judge mangas by their cover, premise or art and thanks to that I was able to dive into Sundome and I can say I was pleased with what I've read.
A warning though, this manga doesn't censure itself, it contains heavy and sexual themes, and it does show them. Things like masturbation, licking each other and even drinking pee is all in here. If you don't think you can handle that, then by all means, skip this one.
If you do, however, this is one fine manga that manages to blend perfectly comedy, romance and drama.
Most of the plot events come from the Roman Group both main characters are members of, as they go on adventures to find UFOs and other paranormal activities. While two of the characters play a major role in the story, the entire group is fun to see, and all have their roles in the story. Besides those characters though, you won't find many more characters in the manga, and that's alright. Focusing just on six or seven people is enough, and you can remember everyone.
The manga is divided between funny and lighthearted, mostly when the group is together, to heavy and grim, when the main characters are left alone. Weirdly enough, even when shifting suddenly from one to another, it never feels forced and it flows pretty well. You'll find yourself laughing with them and crying with them, and, in the end, that's what makes a good manga.
There's only one problem I have with this manga, and it's the art. Most of the times it does work. It's not good, not by any means, but it does it's job and never falls into the "bad" category. Sadly there are times where it fails to fit the tone of the moment. Still, it's a minor rant, has it doesn't happen THAT often.
I also have a minor problem with the ending, has it seemed like the author chickened out of the ending it was going for right when it was about to do it.
All in all, it's an enjoyable manga that is recommendable to every romance-drama fan. Just be ready for the sexual theme and visuals.