I found OTK spanking in "明日葉さんちのムコ暮らし"( Ashitaba san chi no muko gurashi,lit.a son-in-law's life in Ashitaba's family ) serialized in Grand Jump episode 3.
I do not know the story well,but one girl is spanked by her mom.
We can read episode 1 here,
and 2 here,
so we might be able to read episode 3 online in next month...
Original article posted: Wednesday, September 2, 2015
I found pic uploaded on one BBS...