Green Green takes place in Japan's countryside, in a non-descript region with forests and an isolated boarding school known as Kanenone Gakuen (鐘ノ音学園, literally translated as Sound of Bell Academy).
As luck would have it, Kanenone's current administration is considering making the academy co-ed, and in order to see how the change would affect the student body, first and second year girls have been brought to live on school grounds for one month.