It is hypothesized that the two types of social transaction-reciprocal/asymmetric-generally tend to generate and constrain each other, This hypothesis is applied to the Japanese concept of on which as an officially articulated moral doctrine stresses the asymmetric principle. There must be same implicit mechanisms, it is argued, which enable the rule of recoprocity to operate against the explicit, asymmetric principle of on without open clash. Six such mechanisms are identified.