The mobile phone market in Japan has a particular type of user, called a “dual product user,” who uses multiple mobile phones. Compared with other mobile phone users, dual product users possess a high level of consumer knowledge regarding mobile phones. Their ability to process information based on their high level of consumer knowledge may enable them to use multiple products. In fact, during our survey, the mobile phones (iPhones, other types of smartphones, and feature phones) had quite diverse characteristics. In addition, dual product users tended to use mobile phones for gaming. This is likely due to the high telecommunications fees levied on smartphones in Japan as well as the complicated structure of these fees. In assessing these characteristics, users with a high level of consumer knowledge consider their own patterns of usage when using multiple mobile phones for different purposes. These findings will increase the potential for marketing to target those with a high degree of such knowledge.