(sent here by r/japan)
So I'm writing a fantasy in the same vein as the warring states. I think the history and events is fascinating, but I have a question about infidelity and illegitimate children. How tolerable were outside affairs for aristocrats? Were they seen as shameful or something that could be ignored? Also, if a child was blatantly illegitimate, what problems may arise? In this case, a powerful head of a family and clan sired a nekomimi (long story). Originally, I was going to have her be a point of shame for the family, but now I'm not sure that fitting (as it's predictable). So I was wondering if anyone could give me feedback or sources. Thanks.
Are you talking about "sexual relationship outside marriage"? Because polygamy was the norm for those with the wealth to do so. While the main wife's son(s) usually take precidence on succession, there's not much other problems with sons of other wives. If the main wife did not have a surviving son, other sons could inherit no problem. So there weren't really children that were "blatantly illegitimate". They were all more-or-less legitimate.