The Edo period, also known as the Tokugawa period, is the period between 1603 and 1868 in the history of Japan.
Lead character designer, Brian Kesinger, added the notch in Mizu's kasa as a nod to the dent in Boba Fett's helmet, stating that it was a good way to show that she been through previous battles without drawing too much attention to itself.
The show was created and written by wife-and-husband team Amber Noizumi and Michael Green.
Abijah Fowler identifies as British, but is in fact Irish. The conquest of Ireland ended in 1603, the same year the Edo period began in Japan. As such, many would have considered the Irish as British citizens in the period this series is set.
Mizu is 19 years old at the start of the show, making her born around 1637-38.