Calm and rational, Koujirou Shindou is a government official and master negotiator with a well-deserved reputation. While leaving on a business trip, a giant cube appears, and his plane is taken undamaged into the mysterious, indestructible structure. As Japanese authorities try to determine the cube's properties and origins, Shindou meets an otherworldly entity called Yaha-kui zaShunina, who takes the form of a human man. He assures Shindou that the passengers are not in danger and asks for help in negotiating with the human world. Originating from a higher-dimensional universe called Novo, Yaha-kui zaShunina can transfer information between Novo and Shindou's universe through a cube named Kado. Despite possessing these incomprehensible abilities, he does not seem hostile. Instead, he declares that he has come to this world with a single purpose: to "advance" humanity, starting with Japan.