I remember the art not being the greatest but it resulted in a threesome with a dad, his son and his son's friend/bf(?).

I think the friends/couple(?) found the dad's sex toys. There were cuffs. BDSM stuff. They used it. And the dad caught them and taught them how to use it.

There was a scene where they were cleaning the car and the uke was wearing a thin shirt that got wet. Help please. I can still remember the art but the title escapes me. The art style was a little stiff. They had long limbs. Probably one of the older mangas.

It's Hard core heart.