>>149963834
After the Shimabara rebellion, where catholic converts attempted to overthrow the government. Tokugawa either exiled or executed every single european that was on the island. Including hapa children like Mizu. The law stated that no european was to set foot on Japanese soil. With the exception of the Dutch. Who sold them the gunpowder that allowed them to put down the rebellion because being protestant, they hated the Portuguese and Spanish catholics.

Presumably the Itoh clan (who rule japan instead of the Tokugawa in this version of japanese history) have a similar history. Just with Fowler and the British instead of the Dutch.