Shit like this is peak comedy for the japanese. They don't care about the implications. Like the "sister" quite literally planning to kill the wife. She will fail obviously and it will be played for laughs but that doesn't really change the intent. But it will be ignored just like the house.
I don't have much of a problem with that murderous aura, as long as it doesn't have consequences.
What I can’t stand is when a character like that actually goes too far, like in “Komi-san Can’t Communicate.”
There was this girl who was in love with the main girl, even though she was basically already paired with the male lead.
She kidnapped him and was about to bury him. AND NOTHING HAPPENED TO HER!
I don’t mind over-the-top jokes, but… that wasn’t a joke. He was literally going to die.