Oba Netori ~Otto no Shiranai Midara na Kankei~

Rieko Momose the protagonist's aunt.
Tender and matronly, like a true mother always doting on him.
She's fond of him but never thought of him "that way".
Her relationship with her husband is healthy. They have a daughter.
She's also incredibly sensual, giving off vibes that attract other men...
... while her husband seems blissfully ignorant of her needs.

[From DLsite English]