I'll definitely place an interest here. I know much of Japan's history and do indeed enjoy the Sengoku period (though I'm more of a Boshin war kinda guy personally), so it would be most interesting to see how an RP based there would go. 

annnd I've also play Shogun Total War 2 and Fall of the Samurai mucho. 

At a guess I'd probably fill a Daimyo role. Depending on how many folks sign up in the end I'd probably lean towards being a bad guy who supports Hojo and slaughters his disobedient peasants. (unless there aren't many good Daimyo folks, in which case I would be a nice one). 

Also side note for anyone interested in Japan, one of the best books I've read that gives a real insight into the historic factual side from a westerner's point of view is called 'Samurai Adams', it’s about the first Westerner to actually become a Samurai - and is a true story from diaries, records and other shizz made into a narrative format. It’s delicious.

(also I'm not sure your Hierarchy is quite right, the Shogun was actually above the emperor for the majority of Japanese history, especially the Sengoku period. But I'm just being picky and pedantic, so ignore me :rolleyes )