"Think of it from the perspective of their moral standards."
Voryn, I can get culture shock, but JFC. I don't walking into another country and into a stranger's house and start swinging. I would say this is partly Chris's fault for dumping all of this information on him all at once, and not easing him into it, but then again, the brother has no impulse control. Even after assaulting Chris's husband and being shown Chris's outrage at the situation, he still didn't calm down (for Chris's sake).
And they are lucky LUCKY to have found these people. Had it been for me, with the information I now know about these two, I would have them teleported in the middle of the Pacific Ocean.
If the offence was involving strangers then they likely won't have intervened (though they likely wouldn't have anyway due to it being someone else's family matter, this is pathological in Asian cultures but Europeans never had the same view of intervention so long as it was under the law, was by a superior (depending on circumstance), by the wider community or was with permission, but Europeans had different family structures in the first place) under the assumption of differences they don't understand, but by it being his sister the moral norms of his society is still in force, of course this means that the norms will cause conflict when they overlap with other moral systems but you've probably noticed that historical westerners tended clash quite severely with the societies with foreign religions, cultures or ideologies (though secularization, the spread of western moral assumptions in the form of humanism rather than Christianity, as well as westernisation and globalisation have changed that situation quite at bit, and obviously the society has also changed to what we see today as well so the extremes are different). As it was his sister it involves his family and the origin of the offender in moot.
Of course this is a weakness of this moral system, it does not recognise the agency of children over their actions and instead binds them tightly to the greater family unit. Thus Christina's actions and choices are assumed to be her husband's responsibility and he is the one the offence is taken with. Likewise it is a sexist system, the wayward marriage of a daughter would be taken as an affront to family honour while a son doing the same would most likely just be disowned. It is not inflexible, if they hadn't been married when he arrived then he technically could have listened to her wishes and granted permission for the marriage despite everything (though that would depend on him being head of the household and the family would have lost a good deal reputation even if it wouldn't be seen as a slight on their honour, merely a scandal), but that also means that he could have simply taken her back by force and it was probably intended that way by design (e.g. the family get the last say no matter what). The technical offence lays in the fact that it was done without family consent even if the insult may in reality have a far greater number of factors.
I don't know about Europe (if I recall there was only the right of refusal, though you could also make a vow of chastity they could still just redirect you to elderly men who were looking for a caretaker moreso than a wife (marrying older women was a thing but they were rarely over 35, during certain periods a female widow would marry her late husbands brother if he was available, though medieval people at least didn't like that (wider definition of incest), it was a thing still during the first world war), you could also join a holy order in which case you were free from family but under obligations to the order and oaths made to join instead, men seem to have had less pressure but their was nothing wrong with a married couple both under shared vows of chastity and as women were more religious it wouldn't as hard to find someone looking for that, men also had a much easier time living independently of family structures and social obligations though it was still a comparatively difficult life) but in Japan it was also traditional that the family would lose their say over who you married if you were still unmarried by a certain age (I think 25 but that's from memory).
