We have integrated technologies related to virtual social interaction, e.g. virtual environments, visual simulations, and lifelike characters. In our previous efforts to integrate them, the asymmetry between agents and avatars made the systems too complex to be used widely. Another crucial problem we faced is that it took a long time to construct agents that play various roles, since each role needs its specific behavioral repertory. To eliminate these problems, we developed a general-use platform, FreeWalk/Q, in which agents and avatars can share the same interaction model and scenario. We created a control mechanism to reduce the behavioral differences between agents and avatars, and a description method to design the external role rather than the internal mechanism. In the development, we found that it was necessary to prepare several topologies of control mechanism and several granular levels of description method. Categories and Subject Descriptors H.5.3 [Information Interfaces a...