This study served as an attempt to better understand social relationships by using facial expression electromyography (fEMG) analysis. The goal was to be able to visualize social relationships through objective data to broaden understanding of the mechanism of social relationships and social design. This study focuses more on observed daily experiences as a means of comprehending social relationships among the participants and to determine if social relationships can be understood using fEMG analysis. The authors conducted an experiment that compares the results of fEMG analysis with social relationship transitions recorded during a card game called mini-bridge. This is a game played in teams, and it requires that players work in pairs. It can clearly be seen whether the pair is successful in this co-creative relationship by checking the data recorded on video and by seeing what cards are in each player’s hand and how they play the game. During the game, the participants wore electrodes on their corrugator supercilii and zygomaticus major, allowing us to collect data using fEMG (objective results). Using a shared behavior and intentions study from the videos, the intersubjective state of the examinees was graded (subjective results) and compared to the objective results interpreted through the Levenshtein method. The research results suggest the possibility of identifying a social relationship as a partnership by using fEMG with data from the corrugator supercilii. This study will contribute to our knowledge of the mechanism of social relationships, which is needed to develop a methodology for social design.