[@unicorgi]

Some more backstory for you.  

The Oni are ubiquitous in the world in general, but Ronin are largely specific to Burokun.  They definitely started to show up as a direct response to the Oni moving in, but until relatively recently they were basically a human version of the Oni presence.  Which is to say, they were gangs that set up shop in various neighborhoods.  They even used to expect their own kind of tribute and respect.  

This started to change when a brave crew of journalists filmed a comprehensive documentary about them(as they were a fairly unique phenomenon).  The Ronin featured in the documentary gained a kind of internet fame, and several of them started filming their exploits(particularly themselves fighting Oni) and posting them online.  The ones that did started to make some money off of their youtube views, which inspired almost all of them to follow suit.  

As always happens, a big company wanted to monopolize on this revenue stream, and so an American production company hired the original documentarian who made the film, and set her up as the director of a new TV show by the same name: Street Samurai. 

As the show has gone on, the Ronin have become less violent toward the citizens, but if anything even more agressive with the Oni and with each other.  And as sponsors have come into the mix, they've started to get daring and reckless, trying to get fans and online following, to attract benefactors.