What's the psychology behind the common "black hair is a sign of evil" trope in isekai? In our world, black/dark brown is the most common hair colour by a wide margin, so from our point of view, it would reflect absolutely nothing. Is it just some weird, artificial martyr complex by the Japanese authors when a Japanese person is thrown into a pseudo-European, historical setting? Even though in Europe dark hair colours always existed, more in the south, but it's not like they would have been absent in the north either. Of course if two blonds had a child with dark hair, the husband might become suspicious, but that's clearly not the case in most isekai, where it's not the father being outraged but the whole country viewing the black hair as abysmal.