it doesn't automatically imply he is legally responsible for them.
True. But it also doesn't stop the twins from retaliating on him and his "business".
Even if he later goes to the guards and report it as assault and theft, well... He still signed a new contract so he agreed to be responsible and to settle it with him paying them.
Looking at laws will change nothing if he agreed to it (on paper).
He may later try to prove that
his base full of vicious thugs was raided by beautiful twin girls, he was forced to write a contract to appease them with money: claiming responsibility and writing off their debt by a reduced amount of money and paying them extra.
But then,
that'd mean that his thugs are a bunch of weaklings that two girls can take down,
shake down their leader and force him to do whatever they want.
500k or his reputation.
It earns his animosity and is a reason for him to attack the girls and the twins (and by extension even Alan might be attacked) but they fear nothing since they think of the people on this planet as basically barbarians.
It's like they are colonizers with muskets or proper guns and the other side is only holding bows and spears.
Ps: Nobody would care about 5 orphans which are abundant.
Even Alan catching criminals was something not that they wanted him to do, but something they wanted him to fail at doing. And what if the penalty for theft is cutting an arm? Not very nice. I mean possible to fix for Alan and others but still annoying to do and the girls will be shown as an attachment to the MC incapable of taking independent action and that they can't do anything on their own and have to rely on the smarts and powers of the great MC to save the day.