At least he's taking control of the situation I guess. I'm not sure what the best course of action from here would be though.
If they were to run away like they planned, there'd be no way they could get away from law enforcement.
Calling the police and reporting it as self-defense might be the best option, but it's not like the two of them have access to great lawyers (and I'm assuming Aiko's family does have the means to get a good lawyer, which could be used in favor of the mom/against Aiko).