Kanenone Gakuen is an all-male residential school in Japan's countryside. Although an all-male school is nothing new, life may be challenging when there are no female pupils within miles. To improve everyone's psychological health, the school board has decided to try to combine with the neighboring all-girl boarding school in order to become co-ed. Kanenone's boys are overjoyed, while the girls are wondering about how fascinating school life may become if there were more lads around. Before making any major decisions, the girls have been asked to stay at Kanenone for one month as a trial period. Green Green follows Yuusuke Takazaki and his mischievous roommates.