This post is typed verbatim from Keys to the Japanese Heart + Soul, an excerpt from Japan: An Illustrated Encyclopedia with authors' notes at the bottom.
Giri, Reciprocal Obligations
'Giri' refers to the obligation to act according to the dictates of society in relation to other persons. This only applies to particular persons with whom one has certain social relations, however. It is a sense of giri that obliges reciprocity in giving; it compels one to return equal favours to those who have been helpful. The concept implies a moral force that causes one to engage in reciprocal activities, even when a person is not particularly inclined to do so.
To feudal warriors, giri referred to an obligation to serve their lord, even at the cost of their lives, to repay the on received from their lord.
To be observant of giri is an indication of high moral worth. To neglect giri is to lost the trust of others, and to eventually lose their support. Generally, human feelings do not conflict with social norms (as people usually think according to what they were conditioned to believe), and observance of giri does not conflict with ninjou (what one "naturally" feels towards others, love, hate, respect, etc.). However, conflicts do inevitably arise, and must be dealt with accordingly. Today, giri and ninjou are outmoded connotations, but the concept is far from eradication. The concepts are still very important in rules of conduct today, and someone who does not adhere to them may find themselves in difficult positions.
Previously: On, A Sense of Indebtedness
Next: Ninjou, Natural Feelings