Correct me if I'm wrong, but I have a serious itch that this is Hitoshi's wife.

Her Sanae-wife in Hang In There, Kogasa-san is also quite busty, so you're possibly right...

Alright, I'm gonna have to throw up a commentary request, then.

Mizuki Hitoshi said:
「おかあさんもいっしょ」という作品の、携帯配信サムネイル用の画像です。
携帯配信サイトで「みずきひとし」で検索かけるとでてきます。
たぶん(笑)
au携帯だと確認できるんですが、ほかのキャリアだとわかんないんですよね(^^;)

作品内容は18禁なので、よいこはおとなになってから！(笑)

She's from that h-manga that Mizuki drew and Tada translated a while back, Indecent Mother Sex Diary. Really amusing.

But it looks like somebody has a muse drawing this picture. And we can guess who is she.