Sumanai is a Japanese word that refers to a feeling in response to a favor; it includes gratitude, along with sorrow and sometimes guilt for having put the benefactor to so much trouble. The purpose of the current research was to explore sumanai, gratitude, and indebtedness, and their relations to interpersonal orientation and psychological well-being. Results from Study 1 with 115 female Japanese university students confirmed the distinct meanings of gratitude, sumanai, and indebtedness in terms of their dissimilar correlations with other feelings. The results also revealed that when the benefactor’s expectation for repayment was manipulated, gratitude and sumanai, but not indebtedness, decreased with increasing benefactor expectations. In Study 2 with a sample of 179 female Japanese university students, sumanai had a significant positive correlation with interpersonal orientation but did not have a significant positive correlation with psychological well-being. Interpersonal orientation mediated the relation between indebtedness and psychological well-being, but did not mediate the relation between gratitude and psychological well-being. Gratitude had significant direct paths to psychological well-being and interpersonal orientation. An alternative model was also supported; gratitude mediated the relation between interpersonal orientation and psychological well-being. The contribution of gratitude to well-being and interpersonal orientation are consistent with the extant literature, pointing to gratitude’s ability to build and maintain social relationships.