Sewayaki Oku-san de Hito no Tanomi o Kotowarenai Ai-san ni Onegai Shite Nakadashi Hame Houdai no Dosukebe Tsuma ni Nattemoratta

You return back to your hometown after getting accepted into university at age 18,
and happen upon the neighborhood girl who used to look after you when you were young.
She's become even more beautiful, more bountiful, more erotic than ever in the six years the two of you have been apart.
Of course, she's married, but you come to learn that she is unable to refuse requests, no matter what.
Since she was your first love and all, and even now you hold some lusty delusions of being with her, you request sex.

"I can't believe it....but if you ask me like that, there's no way I can say no..."
"Just once though, okay? And this is a secret!"

But alas, more and more hardcore requests were to come...

[From DLsite]