A tendency to prioritize the rights of concerned parties unquestioningly was consequently observed among people around the location of not-in-my-backyard (NIMBY) facilities—a phenomenon which is defined as superior legitimization of the concerned parties. However, this is an intuitive decision that results in irrational goals, such as non-completion of public goods. The multipolarization of concerned parties, wherein two or more concerned parties hold conflicting interests, is hypothesized to induce intentional consideration that inhibits intuitive decisions. High-school students played a simulation game, “Who & Why Game (WWG),” in which they were tasked to deliberate about the legitimate rights to decide the placement of a high-level radioactive waste storage facility as one of four roles; namely, a local resident, an expert commission member, a national majority, or a government agency. Their superior legitimization of the local resident was inhibited when future generations were presented as another concerned party having a conflict of interest with the local resident. Finally, the usefulness of the WWG was discussed theoretically.