夫が突然の蒸発、正式な離婚もできないまま女手一つで息子を育てている双葉。食事の準備、保育園への送迎、そして早番パートと忙しい日々を送っていたが、それが終わって息子を迎えに行くまでの空白の「5時間」だけ…。双葉は〈母〉の仮面を脱ぎすて〈女〉としてパート先で出会った学生バイト・春斗とSEXをするためにひと山超えてママチャリ全力爆走！！職場トイレでも我慢できず時短SEX。母としても女としても幸せ絶頂な日々を送っていた双葉だったがある日春斗に別れを告げられ…。

Futaba is raising her son alone after her husband suddenly disappeared, unable to even get a formal divorce. She leads a busy life preparing meals, taking her son to and from daycare, and working an early shift at her part-time job. But there's a gap of "five hours" between finishing work and picking up her son… Futaba sheds her "mother" mask and, as a "woman," races across a mountain on her bicycle at full speed to have sex with Haruto, a student part-timer she met at her workplace! She can't wait any longer and has quick sex even in the workplace restroom. Futaba was living the height of happiness as both a mother and a woman, but one day Haruto breaks up with her…