Well this is a story of Nanako, a young student who came for the first time to seiran high school with her friend tomoko. There she will be chosen to be member of the Sorority, a very prestigious club ruled by Fukiko Ichinomiya. This provokes the jealousy of many other students who will try to make nanako quit the Sorority. Fortunately she has friends to support her, like Kaoru and Mariko. She will soon discover that she is not the one who has problems, and she will try to help her friends, especially Rei Asaka, which has an ambiguous relationship with Fukiko. Well you can download the manga on lilicious.net. I'll put the link soon!!
If you want to see some images of oniisama e come here to my freshly new site: http://marikoshinobu.tripod.com/