Part I and Part II introduce various results of the unfoldings that are introduced. First of all, what is an “unfolding”? When you cut the surface of a solid and spread it over a plane, you may have a “net” of the solid by this unfolding. To obtain a proper net, it is required to have two important properties; it should be one piece, and it has no overlapping. These simple properties are sometimes quite difficult to have.