Wakai Otoko ni Hamatte Shimatta Part no Okusan no Ohanashi

The story begins with the protagonist meeting Yayoi Seki at his new part time job.

Three years had passed since the protagonist started working part time in the countryside, and after passing his university exam he decided to confess his feelings for his coworker, Yayoi.

Yayoi initially refused but after learning how hard he was working to continue his studies and make ends meet, she began to feel a motherly love for the protagonist.

In the end Yayoi was able to be persuaded to go on a single date, however on the day of the first date Yayoi didn't return home until late at night.

"It's just until he gets tired of you, there's the age difference, and I'm just an ordinary middle-aged woman"

That's what Yayoi thought but when the time came, Yayoi was the one who took action...

[From official site]