Well, it's not so caught up in the moral side of things like School Days. That may just bite it in the ass later on... right now, I'm sort of wishing there are some moral guidelines to be drawn.
Wait... which manga? I've read up to chapter 73 in Kiss x Sis right now and I'm taking a break. The plot turn after chapter 50 was one of the most satisfying developments I've ever read. I'm not lying when I'm saying this is becoming one of my favorite series of all time. To think, originally I was just looking up ecchi material...
Speaking of other ecchi Manga, this has turned my interest towards To Love Ru and To Love Ru darkness. I hope it's got a nice plot too.