A couple longs for a child but struggles to conceive. After visiting the hospital together, the wife, Yumi, is diagnosed with infertility. After much deliberation, the couple decides to ask Yumi's mother-in-law, Hitomi, who lives with them, to become their surrogate. What follows is an unconventional drama filled with forbidden relations and impregnation, as the stepmother becomes intimately involved in fulfilling their dream of parenthood.