Im going to point out the obvious, black eyes don't exist. Even in Japan, its just very dark brown, and I always find it kind of cringy, almost chunni when they make black hair / brown eyes some super rarity. Like even in Europe, what most of these stories are set on, black hair and brown eyes are the majority.
Its like a dude writing a story, and the character name is John Smith or Kim, and people acting like this is the super rare awesome name. Reminds me of that one isekai where the dude names himself after norse mythology and you can see the cringe happening in real time.
Then I guess its not as bad as the nonsense, where a quarter or half mix, somehow has blonde hair , blue eyes, and European features; like genetically thats impossible. Recessive genes literally cannot show up, unless both parents are mixed. Even if the quarter were Japanese and the other 3rd completely European, the individual would still more likely than not have very distinct Asian traits.
Back to this story, my other issue is, no way would this empire allow men to be treated like that even if they are rare. Even if kept as slaves, they would not be allowed to just any woman, especially not soldiers, and they couldn't risk them being broken, because then you couldn't well ............reproduce. In a worst case they would be treated as servants by the elite.