Mari is a shy, studious girl who has neither a boyfriend nor any friends. One day, Akiko - one of the most fashion-conscious and sociable girls in the class - strikes up a conversation with her out of the blue! As the days go by the two become inseparable, with Akiko often cheerily remarking on how they became best friends so easily. Mari has a lot of fun with Akiko and her group, slowly becoming more outgoing despite still being timid and awkward. But she knows, deep down inside, that she doesn't want them to stay just friends forever…
Girl Friends is a completed manga by Morinaga Milk, first published in 2006. It blends romance, girls' love, drama and slice of life. You can read all 40 available chapters of Girl Friends online for free on MangaPulse; the newest is Chapter 35.5, added 2018-02-05. The series is finished, so you can read it from start to end in one go.