When his passenger aircraft is taking off from the Haneda airport, a mysterious giant cube suddenly appears in the sky.
A mysterious person (?) Yaha-Kui Zashunina who comes out of Kado tries to make contact with human race, and Shindo in the cube has to work as a mediator between human and Yaha-Kui Zashunina.
Plot concept: The story follows the protagonist Kojiro Shindo, who is a shrewd negotiator at the Ministry of Foreign Affairs of Japan.