As densely populated as Franconia, Eastern Asia is home to China, the largest and richest part of the known world. Almost all of Europe's landmass could well fit within the ambit of China and surrounding lands, and thus it is not surprise that it is the greatest prize that any conqueror could ever want to win — and thus has been coveted by the ferocious barbarian tribes to the north.
Eastern Asia can pretty much be the richest region by virtue of the net tribute gained from conquering it. For not only is its unification bonus the highest ever in both campaigns, the average tribute attained for every one of its territories is also the highest. The factions which surround Eastern Asia (China, Mongolia and Japan) can easily set themselves up for global supremacy if they want to do so.
Even so, there are problems. Compared to its tribute score, Eastern Asia has only three supply centres, making it somewhat poor in terms of human resources for prosecuting warfare abroad. However, the most notable resources which Eastern Asia hosts which simply can't be found elsewhere are bananas, porcelain and tea. In addition to resource flows, these three rare resources can be quite powerful — they make all your units tougher, as well as protect them from attrition. Buildings are also benefitted by tea's bonuses. Because these are located well within the Chinese sphere of influence being so close to both starting positions, China should make it a priority to claim them all once the Mongol invaders to the north and the Turks in the Middle East are pacified.
Resource count 
The homeland of the Japanese people for more than three millenia, Japan is located at a strategic juncture between the two islands of Ezo and Kyushu and the Korean peninsula at Scilla, serving as an alternate route between eastern Asia and northern Asia.
The mountainous north of Korea is well known for its prized iron deposits. Control of Goguryeo is essential to controlling the northern reaches of the Yellow Sea, as it is linked to the Yellow River Basin and the Pearl River by sea, aside from being neighbours of Manchuria, Bakjae, and Scilla.
The second largest territory in Korea, this hilly territory affords the local inhabitants natural fortresses from which to resist foreign invaders — a fact not lost on the locals who have successfully resisted attempts by the Japanese and Chinese to subjugate them, either through the neighbouring territories of Goguryeo and Bakjae or via Japan and Kyushu.
Yellow River basin
Once the beating heart of the Chinese civilisation, this part of the world has been overrun by northern barbarians pouring out of Mongolia and Manchuria for almost half a millenium, who have ensconced their warlords as the kings of the local Chinese populace.
At first sight, this harsh and parched land may seem undesirable. But looks can be deceiving: rumours of a dragon's graveyard amidst the shifting dunes have attracted scholars and treasure seekers, but few have returned with anything of substance to show yet alone tell of.
Despite its arid and inhospitable climate, the Tarim Basin is a vital crossroads for merchants and monks alike passing east and west on the Silk Road.
The latest land to be colonised by the Japanese people, Kyushu has a subtropical climate that appeals greatly to many of the people from the far north, making it ideal especially for the production of food if it can be developed.
This extremely fertile plateau guards the strategic passes that lead from the coastal plains into the mountains of the south and west of China. The territory is also crisscrossed by four rivers, hence its name and so can provide ample food supplies to support your troops on expeditions.
These mountains mark the boundary between China and India, and while difficult, inhabitation here is not impossible.
Home of the Uyghur tribes, this land is also known for the production of one of the world's prized fabrics - Silk.
Headed by the great trading port of Guangdong, the Pearl River region is one of the more valuable territories which form China, blessed by ample farmland which has helped in supporting an industry dealing with high-quality ceramics. The island of Hainan in this territory is also close by to the two southern lands of Greater Yue and Cham, making access to these two lands from China a feasible prospect.
Formerly part of the land of Yue, this territory was annexed by Chinese refugees fleeing the depredations of Turkic peoples to the north, and has now become the main focus of Chinese resistance against the northern barbarians. Wu is cut off from the rest of the Chinese lands by the Yangzi to the north and the Pearl River to the south, and its climate and well-irrigated plains make it ideal for the cultivation of citrus.
Connected to Wu in the north, and Bagan and Cham to the west and south, this territory varies in geography and climate, with massive mountains to the north and west, and treacherous swamps to the south.