The reasons? It’s quite dated, 1989 (PWOAH!!!) so the art from that period as expected (at least from my experience) tends to be more old fashioned. The character designs typically have darker features, 90s fashion (big shoulders were in at once stage hahaha) and more masculine frames to the characters (particularly the stronger one of the pair). The last reason why I would not have naturally read this is because it has rape in it. ::shudder::
BUT, I have read it now as Katherine over at Yuri no Boke mentioned that this is a must read for all yuri fans (she mentions it in a post that reviews another manga – Love Slave which I will probably check out later).
Akari Mizunashi over at Baka-Updates recently wrote a good summary so I steal hers (if she doesn’t mind):
Love at girls’ schools has long been an entirely noncontroversial staple of girls’ fiction in Japan for one reason: the accepted idea that such affection was a phase that would be grown out of after entering the mixed-gender world. Moonlight Flowers reads as a sequel to all those innocent girls’ school romances, a sequel where the women don’t shed their “fake love” and are forced to learn what Japanese society really thinks of lesbianism. It’s yearning and feminist and beautiful.
That said, because it is 1980s Japanese feminist, man-hating sentiment runs thick in this manga. Men are described as wanting nothing more than to completely dominate women, which is why they hate lesbians, who have no need for men. However accurate this is for the time and place, it does give a slight unpleasant flavor to what would have otherwise been a perfect josei yuri.
I’m pretty much of the same view as her. It’s a decent read but I wouldn’t quite call it a must read. On the otherhand, I quite liked the second story ‘Midnight Flower’ which is a side story of one of the main characters that tells how she came to terms to accept that she’s a lesbian. In terms of less fluffy works, the most I can probably handle is Pieta (a must read!!).