Shoujoai dating game
Gonna have to recommend Girl Friends by Morinaga Milk. It's very realistic, in that nobody is gay or in love right off the bat, except for the main character.
It deals more with the two main characters coming to terms with their sexuality and their relationship. it follows the story of two girls falling in love - Fumi who is a lesbian and Akira (A-chan) who is as of yet portrayed as a naive asexual.
Manga No Tsukurikata Hanjuku Joshi is a really cute story about 2 girls in high school. Quite frankly, this is a must read for yuri fans I think.
There are some(read as a lot of) relatively graphic sex scenes throughout the manga.
I'm not terribly fond of the "everyone is gay" worlds anymore than I am of the "everyone is straight" worlds. that's actually all I can think manga series (which has been animated into an 11 episode series) called Aoi Hana is probably the best thing i can think of- then again i dont read or watch anime that often.
The term “Shoujo-Ai” is never used in Japan as a type of category of anime. But in the West, it categorizes anime that tells non-sexual relationships between girls, or simply used to categorize anime with girls love, be it subtext or not.