Though mothers in Japan aren't expected to bear the entirety of the family's child-rearing burden as in decades past, author Lisa Katayama says the strain still falls largely on their shoulders. | GETTY IMAGES Soon after enrolling her daughter in hoikuen (daycare) during a summer stay in Tokyo, Lisa Katayama noticed her 4-year-old adopting a new sense of self-sufficiency at home: She began folding her clothes before putting them away, finished most of the food on her plate and used just the right amount of soap when washing her hands — a dramatic change from her daughter’s previous habits. Katayama, who is of Chinese and Japanese heritage, grew up in Tokyo but now raises her two daughters with her husband in San Francisco.…