samurai This foreigner is the shogun's son?

The shogunate in this alternate history have taken a less isolationist approach while maintaining some culture without room for negotiation. The leading head long before he was made shogun had been permitted to study abroad and bring back servants, a small event his father thought would lead to at most a few illegitimate heir so far away it wouldn't be a problem regardless of reckless action, what wasn't expected was for his son to comeback with a pregnant woman of far darker color who the young man deemed worthy of a concubine. Rather fortunately for public reputation the poor woman had died during birth but the resulting child was a son, politically and socially there were a few foreign courtesan or a trade in citizens but the stigma for mixed blood kids left a very small subset of the population. The shogunate heir having a male child is usually something to celebrate but of such dark skin and foreign features was an uproar that even the emperor of Japan couldn't look past, it was decreed that the child would never make a public debut and while still subject to the advantages of being the next heir after his father, if the shogun has another son then the first born would lose all rights to the position.

The mix blood boy was quite fortunate as no matter how much the new shogun tried, no children were ever conceived that lived longer than maybe two years. Now nineteen and with a war brewing between a rebellious band of ronin, his father is off to gather allies while he is taught to navigate a small section of the outside world and gain small time experience in both live combat plus a respectful social acumen. The problem he has run into within his first month is his smitten nature with the emperors daughter who seems more inline with the ronin than the powers that be, the government wishing to slowly expand beyond Japan while the princess and ronin see a longer future by upholding older more xenophobic beliefs leading to an inherent dislike to the clumsy boy she calls the ugly Oni than his name.

(It would be fun switching it up from the usual European knight motif plus what may seem like alternate historical fiction could become low/high fantasy with small acts of magic and powerful weapons beyond the basics steeped in Japanese culture and mythology. The prompt seems quite clean but I can promise a lot of wonderful ecchi content, a healthy raunchiness, and so much more beyond a good story. As always, indulge a little~)