This separation has historically led to a family structure where the mother and children form an emotional unit, while the father remains somewhat on the periphery. In Japan, this has contributed to the phenomenon of rusu-fufu (absentee husbands) and the "retired husband syndrome," where wives struggle to adapt to their husband's presence upon retirement. In this structure, the mother often invests her emotional energy primarily in her son, deepening their bond at the expense of the bond with her husband.