How many books does it take to write a book?

This many. For historical fiction, at least.

And that’s not counting the vast array of internet resources I had at my disposal or the copious amount of time I lived in, worked in, and traveled around Japan.

It’s like Game of Thrones, but with ninjas

An island nation torn apart by warring houses, each vying for control of the throne. House O occupies the capital. An old friend of House O, the lord of House T from the north, turns on O and marches to remove him from the throne. On the cusp of victory, the lord of House T is mysteriously assassinated. Following a succession of betrayals and illnesses, T’s fourth son takes over the house. His poor leadership skills and inability to rally his house leads to its total dissolution, as internal factions split off to support neighboring houses. The House of T, long the ruler of the north and favored lord to win the game of thrones fades into the mists of time.