Mary was frustrated by her busy husband who wouldn't let her have sex often enough. After being diagnosed with low sperm count at the hospital, she still had a slight chance of getting pregnant but without any miracles happening, things were looking grim. One day, when her father-in-law came to visit Tokyo and stayed overnight, Mary saw this as an opportunity to finally address her concerns. Her father-in-law seemed excited about spending time with his grandchild too, so she couldn't bring up the topic easily. However, fate intervened when he accidentally discovered her predicament. In an attempt to help out, he secretly drugged Mary with an aphrodisiac. When confronted by her father-in-law about whether or not he truly enjoyed having sex with his son, Mary felt compelled to prove him wrong and ended up being fucked by him instead. As her lust intensified under the influence of the drug, Mary found herself increasingly drawn towards her father-in-law rather than her own husband.

多忙を理由になかなかセックスさせてくれない夫に不満が募るメアリー。病院では精子が薄いと診断され妊娠の可能性は0ではないが、奇跡が起こらない限り難しいという状況になってしまった。そんなある日、夫の父が東京へ遊びに来て泊ることとなった。義父も孫を楽しみにしているだけあり、なかなかその悩みも打ち出せなかった。ひょんなことから息子の事情を知ってしまった義父はメアリーに媚薬を仕込む。義父は息子とのセックスに本当に満足しているのかと問う。親として責任を取ると言いメアリーを犯し中出しする義父であった。義父の度重なる媚薬責めにより発情してしまったメアリーは夫ではなく義父を求めるようになっていった。