This study confirmed structural causal relations among concepts such as characteristics of service-offer, satisfaction, trust, affective commitment, and loyalty and surveyed mediating roles of affective commitment. The results are as follows. First, Customized service and service reliability influenced satisfaction while service competency did not. Service reliability affected trust while customized service and service competency did not. Second, satisfaction influenced trust and affective commitment but not loyalty while trust affected affective commitment and loyalty. Third, affective commitment influenced loyalty through the mediating role. The results mean that the seller-buyer relationship is a dynamic relationship. Finally, we discussed the role of affective commitment and the strategies of affective commitment development, and suggested future studies.