Shinobi Densetsu takes place in a fantasy world, largely mocking Feudal Japan from medieval times up to the 1800/1900's. However, many times you will encounter zones that do not fit in this description, and because of that, they will be introduced appropriately in the game.

The Civil War

After the emperor Koshiro II deceased mysteriously with an unknown disease, the island of Aoshima was divided into small factions fighting against each other. Not only the emperor was young, he left no successors. As Aoshima's laws only allow a son or daughter to heir the crown, the country was left without a leader, and feudal lords started invading neighboring provinces. The thirst for power spreads to the whole island's territory.