Divorce rate in Japan is increasing these days as well as in the U.S., but it is still lots lower than that of the U.S. This is because of the difference between American and Japanese people in considering marriage and divorce.
In Japan, marriage has been considered as one of four biggest events during one's life time("kankonsousai" =coming-of-age ceremony,marriage,funeral, and worshiping). It is not just a matter for new husband and wife. It brings and creates a connection between the entire families of both wife's and husband's family members. In Japan, husband/wife usually calls his/her father "otousan", mother "okasan", and siblings "onisan/onesan" as well as his/her mate. Marriage usually means to truely become the child of mate's parents. This also means that, for parents, marriage of their child would bring them a new child. Therefore, parents are introduced boy/girl friend by their child, they would examine that person carefully. Sometimes, this causes severe arguments and conflicts among the family members, but if a couple could overcome this situation, they would be strongly tied each other, and if they could not, they just break up and woul not marry. Therefore, the average of marriage period in Japan is longer than that of America.
While marriage is seen as an honorable, and even sacred event in Japan, divorce is viewed as a very dishonorable and shameful thing to do. It is thought that divocing would show that that person is not a good judge of character. This is another reason why divorce rate is lower in Japan.