The chick is used to being treated this way. The impotent husband lost her at cards. That's why they've been pulling her like a bitch all day long. And the harder the stake, the harder they drive it inside. Only the pussy is already so used to the new masters, to the abundance of milk - that she does not want to go back.
Till the end it's not clear, is it a comedy, a thriller or just a specific Japanese porn, with a weirdo hero. But it is interesting to watch. Especially surprised by the large breasts of a stranger, I thought the Japanese do not have these.