In the “Future Design of Yahaba Town 2060” introduced in Chap. 6, the current generation and the imaginary future generation were divided into separate groups for discussion and, in the final session, both generations negotiated and reached an agreement. However, this final session was marked by such intense debate that it could be described as a clash between the two generations. I became concerned about the potential lasting impact of this heated debate, especially considering that the participants may have known each other in the small town. As a result, I began to explore changes to the framework for negotiation between the current and imaginary future generations. This led me to consider the Iroquois mechanism described in Chap. 5.