4.12 out of 5 from 155 votes
To my knowledge, all manga authored under Morinaga Milk are shoujo-ai/yuri oriented. These two in particular involve relationships between high school student girls. Although Kuchibiru is an anthology, and turns the heat on much higher than Girl Friends, neither lacks first love between girl & girl and the random occurences of daily school life. If yuri is your thing, give the other a try!
Both from the same mangaka, Kuchibiru Tameiki and Girl Friends obviously share the same general visual style. One of Kuchibiru Tameiki sub-story also feature two characters (Nana and Hitomi) who could easily be considered the inspiration behind Mari and Akko from GF. There's no doubt in my mind that if you liked one of them, the other is absolutely a must-read for you.