I think there’s a season 3 in the works could it be added to this website. Apparently this was a combination of season 1 and 2.
During the construction of the Kurobe Dam, an ancient artifact was discovered, and so the United Nations Kurobe Research Institute was established. Intellectuals from all over the world gathered to study the object, and the children of those researchers attend Mt. Tate International Senior High School, including the institute head's daughter, Yukina Shirahane. In the summer of 2016, a lone samurai once again awakens.