People communicating through machine translators cannot tell what the purpose of their communication is or what other people are thinking because of the poor quality of translation services. If they are able to share their understanding within a "common ground" like a communicative or behavioral protocol, they can overcome their difficulties in communication, and we can improve information systems to help them improve mutual understanding. We designed a multilingual participatory gaming simulation, and conducted multilingual gaming experiments with Japanese and Korean participants. We extracted the protocol for conversation with mistranslations from the game logs and designed an agent to support conversation. Then, Japanese and Chinese played it and we observed and analyzed the behaviors of agents and the interaction between players and agents. Consequently, we obtained two main sets of results: (1) an agent function that notified players of the time that had elapsed since the conversation had broken down effectively speeded up their negotiations and achieved more active communications. (2) Tagging by participants was difficult and ineffective in leading to specific protocols and conversations when mistranslations occurred.