Seigo and Miki, married for two years, were engaged in fertility activities during their most fertile time before ovulation. They had been saving up his sperm for one month prior to increase their chances of conceiving. Meanwhile, Miki's older sister Mina lived nearby and longed for a child but struggled due to her husband's erectile dysfunction and busy work schedule. Determined to get pregnant first, Mina teased Seigo by showing off her bare breasts protruding through her clothes on the day they planned to conceive. She then proceeded to steal all the stored-up semen he could offer, leaving him helpless against her seductive advances...

結婚生活2年目のセイゴとミキは排卵日直前の妊娠しやすい時期に合わせて1ヶ月禁欲して溜めた精子を中に出すという妊活をしていた。近所に住むミキの姉の未奈も子供を欲しがっていたが、夫のEDと仕事の多忙でセックスレス状態になっていて…。妹よりも先に妊娠したい未奈は、妹夫婦の子作り予定日に乳首が浮き出るノーブラ姿でセイゴを誘惑しにやってきて、我慢してやっと溜めてた精子を根こそぎ奪っていくのだった…。