L to R (Western Style). The mysterious Builders have brought humanity to the edge of extinction; can they be reasoned with, or must they be destroyed? Aki Shiraishi is a high school student working in the astronomy club and one of the few witnesses to an amazing event—someone is building a tower on the planet Mercury. Soon, the Builders have constructed a ring around the sun, threatening the ecology of Earth with an immense shadow. Aki is inspired to pursue a career in science, and the truth. She must determine the purpose of the ring and the plans of its creators, as the survival of both species—humanity and the alien Builders—hangs in the balance