that's not what happened. the last couple doesn't live with the other 2 couples.
they still did it in the kotatsu in front of eve
First, eve's dad gave his lover a handjob, under the table, in front of eve. it's a bit wild but there are worse things.
Second, she went to bed before they started having sex, but then she walked back in there and they tried to cover it up. (because fucking in your own home is something you're allowed to do, even if you have kids)
Third, I don't condone the handjob in front of the child but they didn't get caught so oh well.
The last couple annoys me,,, fucking in the living room in a house full of little kids?? Eve's dad is a pig!