サークルdiletta/木村寧都が描くFANZA同人コミックで5万部以上売り上げる人気作品を実写化！主人公・脩平の住む古いアパートの隣室には、シングルマザーの杏子とその息子・大晴がふたりで暮らしている。ある日、困っている大晴を助けたことがきっかけで杏子と仲良くなり、晩御飯をごちそうしてもらえることになった。隣家で和やかな時間を過ごしていた脩平だが、ひょんなことから杏子のオナニー事情を知ることになってしまい、うっかり勃起してしまう。脩平は焦るが、なぜか杏子が股間に手を伸ばしてきて、勃起したチ○ポを擦り始めた。アニメに夢中になる大晴に気づかれないように互いを愛撫するふたりだったが、いよいよ歯止めが効かなくなり…四畳半一間アパートで、連日汗だくになるまでヤリまくる！

A popular FANZA doujin comic by Circle diletta/Kimura Neito, which has sold over 50,000 copies, is now being adapted into a live-action film! In the old apartment next door to the protagonist Shuhei lives single mother Kyoko and her son Taisei. One day, after helping Taisei when he is in trouble, Shuhei becomes friends with Kyoko and is invited to have dinner with her. While enjoying a peaceful time with his neighbors, Shuhei accidentally learns about Kyoko's masturbation habits and gets an erection. Shuhei panics, but for some reason Kyoko reaches for his crotch and starts rubbing his erect penis. The two caress each other, trying not to be noticed by Taisei who is engrossed in his anime, but eventually they can no longer stop themselves… and they have sex day after day until they are drenched in sweat in their small 4.5 tatami mat apartment!