Nobunaga unites Japan, and probably will try to invade Korea and Formosa shortly thereafter. He will also continue to permit innovation, especilaly in warfare, so Japan's Red Seal Ships will be more numerous and more advanced. It is possible they begin to send vessels to trade as far as India and might try to colonize various islands in the Pacific or the eastern shore of Siberia, possibly even Alaska or down into Oregon Country. If technology is allowed to progress you could also see Samurai evolve into some of the finest dragoon/cavalry on the planet. After the unification I'm not sure what happens specifically but if the Japanese remain open to the rest of the world they are potentially a powerhouse by 1800.