Nishiyama Sana is 38 years old and a mother of two children, marking her 11th year of marriage. This spring, her youngest child will start school. Though she was able to take a breather after a busy life of work and childcare, she suddenly began to feel a sense of emptiness. "Ever since giving birth, I've been putting myself on the back burner..." Marital relations are a bland affair, completed quickly while the children are asleep. When she realized she had been living as a mother for about 10 years...