A multi-method approach was used to examine whether and how companion animals (CA) affect subjective well-being and social networks of Japanese people. In Study 1, a mail survey with a probability sample of 1250 Japanese adults over 40 years old showed that (1) female owners' attachment to CA negatively correlated with subjective well-being, and (2), although younger (under 65) CA owners had more close friends than non-owners, this tendency was reversed for those over 65. In Study 2, in-depth interviews with 27 adults showed that (1) female CA owners reported lower subjective well-being than non-owners, (2) although CA owners were generally successful in interacting with strangers through CA-related behaviors such as dog-walking, those relationships were unlikely to become close, and (3) in contrast to the owners' tendency to portray themselves in positive ways, most non-owners described CA owners negatively, such as being lonely or bad-mannered. Based on the present findings, which sharply contradict those of previous studies in the western societies, future issues are discussed.