Manufacturing companies encounter many uncertainties in planning long-term strategies for making their business sustainable. As a decision-making tool in the business world, scenario writing is prevalent for exploring various business strategies by drawing various situations that might unfold in the future. The purpose of this paper is to propose a method for supporting the design of scenarios for planning long-term business strategies. In this method, such scenarios are described using existing sustainability scenarios. The method intends to help companies' strategists describe business environments by reusing and extending descriptions of sustainability scenarios. A scenario about solar panel business is described using the proposed method. The results illustrate that the method succeeds in describing detailed business environments from an existing sustainability scenario, and finally, obtaining several business strategies based on the business environments. In addition, our method clarifies the logical structure of the scenario, thereby enabling to review rationales for deriving those business strategies.