Rei comes to help support her emotionally vulnerable pregnant daughter, easing the strain at home. But for her son-in-law, whom his wife has even forbidden from masturbating, his alluring mother-in-law is unbearable temptation. One day he secretly watches Rei bathe, too captivated by her body to realize she has noticed him. Seeing how desperate he is, Rei offers to relieve him with her hand, opening the door to a forbidden affair that escalates into repeated breeding sex.