After her husband's income falls, Hikari moves with him into his father's home. Her father-in-law welcomes them, and the couple begins trying for a baby. When pregnancy never comes, her husband gives up and stops having sex with her. Her father-in-law has been secretly watching. One day he attacks her, then begins demanding her body almost every day, ejaculating inside her whenever she climaxes. The relationship continues for four years until profound changes appear in both her mind and body, ending in pregnancy as the title reveals.