As robots have been increasingly involved in human lives I modern society, it is necessary to further develop the robots that give positive impression to human. Therefore, we pursued a collaborative project in which Japanese and American university students designed and developed kawaii robots. Before and after the collaborative work, preferences of kawaii attributes were also evaluated by a questionnaire. As a result, we obtained eight different robot pairs. In addition, we performed cluster analysis using the questionnaires on kawaii preferences and obtained clusters of participants before and after the collaborative work. Finally, we analyzed the relationship between robot designs and the clustering results. The cluster analysis shows that more than half of the participants did not change their kawaii preferences, while some of them did especially those who did not have preconceived images of kawaii robots. Therefore, we concluded that participants developed a deeper understanding about kawaii after collaborating on this project about the diversity of opinions people have about the concept of kawaii.