Okaa-san to no Himitsu ~Kekkon no Aisatsu ni Ittara, Senjitsu no Deriheru Jou Deshita...~

Osanaita Taro has a girlfriend, Sayoko, whom he's been dating for three years. He proposed on her birthday, and they happily became engaged.

―――But the afterglow of happiness was short-lived.

“Once you're married, you won't be able to do anything! You better get your fill of fun while you still can!”

Feeling strangely persuaded by his colleague's words, Taro ended up booking an escort. There, he met the sex worker “Emiri.”

His fling with her would drastically shake up Taro's destiny— Because “Emiri” was none other than Sayoko's mother, Kimura Asako...

[From official site]