Would they actually get revenge when Mari needs hospitalization?
Basically the parents couldn't get the boat started, so they figure, well in the mean time, let's just get revenge on them. But by doing so, this puts Mari in further danger, since she is not hostage material, which the gang can use to desperately bargain for, in order to survive being killed.
So it seems that killing her off in the original makes the revenge more logical, than here, since her remaining alive, makes her a target hostage if they decide to take revenge. Unless I am wrong?