People engage in social coordination without explicitly communicating when they are conflicting over spatial resources, e.g., a shop clerk who yields to customers the best place to view products. In this study, we proposed a method that achieves such social coordination with a robot. Our idea is that the social coordination between two agents can be represented as utility-maximizing behavior for joint utility rather than just by a single agent utility. That is, given that each agent's reasonable behavior can be represented as utility-maximizing behavior for single agent utility, we model each agent's plans for himself as well as for the partner agent. Moreover, superiority relationships exist in this joint-utility computation. Since each agent knows such superiority relationships, social coordination can be modeled as utility-yielding behavior based on informed superiority. We specifically focus on looking-together situations for which we developed a utility model. With simulations, we investigate whether the above joint-utility-based modeling successfully reproduces social coordination in looking-together situations. We conducted an experiment in a situation where a tele-operated robot and a customer together look at products in a shop environment. Our experimental results show that our proposed method enables the robot to socially coordinate spatial resources, yielding significantly more thoughtful, less-self-centered, and appropriate impressions than the alternate robot.