I think you need to take a step back because you're nuking it.
Here is the entry. As you'll note it's about forms of
humor related to reception with the audience. Humor itself playing on the inherent absurdity of things.
In this case:
On aka just in settling debts.
Gimu aka offering service if nothing else in settling debts justly.
Giri aka be responsible in managing your obligations.
Ninjo aka empathy and looking out for the other guy.
Is or is not the vast majority of Ranma 1/2 humor an over-the-top version of either doing what the average person would want to do instead of following these and otherwise more or less mocking them? So do or do we not have that kind of humor related to that, and is there or is there not a viable question of its ability to work cross-culture?
Also don't nuke of their "morals" too much. Right up to WW2 the Japanese were in a Feudal system where the elite could cut the peasantry down for minimal reasons. Think of them more like the Greeks with Attica's, which includes Athens, 19 to 1 slave to master ratio. They might philosophize on the nature of justice, etc. but reality ain't exactly cheery. Sparta's being along the lines of 7 to 1 for comparison, and that's just scraping the tip of the iceberg.