Rannarou wants to marry her boyfriend but he's hesitant about marriage. She decides that if she gets pregnant, he'll have to propose! However, there's no sign of him agreeing anytime soon. Then she notices her older sister; married several years and already had multiple children. Her sister was previously married but didn't get pregnant during that time. But since remarrying, she has given birth numerous times. Inspired by this, Rannarou hatches a plan to seduce her brother-in-law and convince him to creampie her repeatedly in hopes of getting pregnant quickly...

今彼と結婚したい蘭々、でも彼氏は結婚に消極的。妊娠したら結婚できるハズ！と企むがさっぱり授かる気配がない。そんな時姉が結婚数年で何度も出産しているのに目をつける。姉はバツ１の再婚で前の夫とでは妊娠しなかった。しかし今の夫と結婚してから何度も出産している。「義理兄にたくさん中出ししてもらおう」悪魔のような妊活が始まる・・・