Rokugan is the Japan like setting of Legend of the Five Rings. It was briefly an official Dungeons & Dragons campaign setting via the third edition version of Oriental Adventures. It was a third party D&D setting for a bit longer via Rokugan d20 after Wizards of the Coast lost the rights to the setting.
There are nine major clans in Rokugan, with seven original clans and two added on later. There are also many minor clans that no one gives a shit about. All of them were
given their rented land by the (Emperor), in exchange for basically making him superior to everyone else. The Emperor has declared that the entire world is his to claim. The citizens and rulers of the Burning Sands and Ivory Kingdoms are still pretty salty about the whole thing.
Firearms exist in this world but in Rokugan nobody uses them. There are few things that the clans of Rokugan agree on, but one of them is a hard "no-guns" policy. Anyone caught using a musket is a dead man walking. This is a major difference between Rokugan and Real Life Japan where the Samurai bloody loved guns and within a few decades went from having no muskets to hundreds of thousands.