So, having recieved the challenge I did, I made several different starts as different Daimyo's of the time - Takada, Hosakwa, Otomo... but here's the clan I decided on - Uesugi.
The Uesugi clan is an interesting choice historically speaking; they survived the Sengoku period along with the Muromachi, though at the time of EUIV's start, they technically weren't in charge of the lands they governed, and weren't until five years after the start of the game. While provincial governors in the Kanto region of Japan, they were still under the rule of the Deputy of the Shogun, before an execution of a family member at his hands lead to them kicking him out and practically strong arming the Shogun into making them the clan in charge of Kanto.
However, this is not the original timeline. On November 11 of 1444... the Uesugi rose up and overthrew the head of Kanto, installing a new one on the throne... with the permission of the Shogun of course. The new Daimyo - Noritada Uesugi - was an able man, with very good stats and still in his twenties at the time, and most importantly, an Uesugi. The stage was set for the Uesugi to rise.
This is Japan in the last months of 1444. In the last moments of peace the Islands will see for decades to come, as the clans begin to wage wars within the realm of the Shogunate itself. The Uesugi are in a very delicate starting position, and one that is surrounded by enemies. The Shogun holds their rightful province of Musashi, and views them as loyal subjects on one hand while denying them their claims on the other. His tax collectors ravage the coffers of the clan, reducing our income to a sliver of that of the others.
To the north, two hostile powers border us as well - the Date clan clings stubbornly to their cold lands, looking enviously at the holdings of the Uesugi, while the Shiba wish to expand their foothold in the northern lands. Both will need to be crushed before the foolish Shogun can be overthrown. The men of those lands, and the coin they provide will be vital to maintaining the economy of the clan lands.
However, to the south, is where the clan's expansion shall focus at first. Why? The Takeda are weak at the start, and have no allies, but control the most vital of resources that will allow us to fund our armies - Gold. Gold in EUIV is a double edged sword, as it provides a very solid amount of income at the price of rampant inflation if it consists of too much of your income. It'll be the way to make sure we can actually fund the massive armies we need to keep the Shogunate from destroying our lands, when we get too large. The Takeda simply cannot be allowed to remain independant - with their massive income, they can overcome the forcelimit of troops without too much trouble. So, I send an alliance offer to the Imagawa, recieve an answer, and then attack them.
The Takeda ally with the Date just before hand, but they'll do nothing to impact the war as the combined Uesugi and Imagawa forces crush the Takada armies and then lay siege to their lands. Within a year, the war is over.
This was run with no claim or cause, so I took a stability hit, and when I got a claim on the Date's only province, we had a truce. Normally, there'd be a -5 to stability as I had a truce, but I was already at -2 because of that earlier war. The bottom limit is -3, so why not?
It's a short war which completes me a mission, and now the Uesugi have five provinces. We are easily the power in northern Japan, but no where near strong enough to challenge the Shogun's massive armies.
A nice event fires. I'll take that extra military tech thanks.
I forgot to take screenshots of a war I was dragged into by my allies, but the result was about as good as it could be considering I lost my entire army to a massive stack. The Shiba clan was forced to cede the last of the northern provinces to the Uesugi in a peace deal, along with Etchu. Our rule of the Home Island's northern half cannot be contested.
The Imagawa served their purpose. After insulting the mighty Uesugi, they deserve their fate. However, more important that achieving a stranglehold on the most of the island, is upgrading my Military Tech to 3. Let me explain a bit why this is so important.
The Chinese tech group starts at Level 2 in all techs, while Western Europe and Eastern Europe (and the Ottomans) all start at tech 3. The tech cost for the Chinese group is also absurdly high, and the first couple of tech groups give frankly amazing benefits needed in the long run. But the early levels of military power will be vital. Why? It all has to do with the Japanese traditions verses the Daimyo ones. The Daimyo traditions are based on government type, which provides a nice bonus to your military - +10% to Infantry Combat Abilty and to Morale - while not providing much else. The Japanese traditions on the other hand, grant
+15% discipline. Even with the morale boost provided by the Daimyo group, one to one, your troops will lose badly to the Shogun's at tech level 2. Your morale isn't high enough to soak that extra damage that discipline provides. However, the jump from tech level 2 to 3 gives an awesome boost, when combined with those you have. Suddenly, I was rolling in 3.5 or so Morale compared to my opponents 2.3 morale. Even with inferior numbers, this would allow me to out endure any of my foes on Japan, no matter their numbers, with a decent general, with close to even numbers
The rapid expansion I'd undertaken in just a decade though, had worn down my manpower and raised my Aggressive Expansion rating to god damn insane levels, over -200 to opinions of my clan. I needed time to build myself up more to be capable of actually fighting the Shogun. It'd happen soon, I could promise you that. I also released the Date as an independent Vassal, to give me that extra time I needed before the Shogun would declare war to annex me.
This event helped out a lot.
This one didn't, especially after a major war to destroy the Shiba clan to raise my Force Limit to a point that I could support an army capable of fighting the Shogun. Then, the event I'd been dreading happened. The Shogun declared war on me to annex the realm of Uesugi. It was a bloody conflict, with the entirety of Japan dragged in against my armies. Thousands of lives were lost in the first disastrous engagement of the war, and I nearly bankrupted myself recruiting mercenaries to replenish my army to the point of being able to take on the Shogun with my massive doomstack. Sadly I forgot to take screenshots of these engagements, primarily because I wasn't expecting this fight until about a decade later in game. But it was rather short, after my first defeat. The Shogun's armies foolishly split up to siege my provinces, and my large stack wiped out each one in turn before starting to be used to seige the provinces the Shogun held. If he lost all his lands, he'd be forced to the negotiating table.
By 1465 and into the early months of 1466, there was no question who would win this conflict with the shogun. He'd taken on the mighty armies of the Uesugi clan personally, and been defeated by a peasant soldier elevated to general after one fo the Uesugi's many wars in the conflicts earlier. It was just a matter of time before the walls of Kyoto itself fell to the clan who were destined to become the true rulers of Japan. The Shogun himself was dragged before the Emperor by the Uesugi diamyo, who held a sword to above the Shogun's neck as he signed the treaties that would end the war, a tanto in his left hand. There was no doubt that he had shamed his family name, honor, and legacy.
The terms were simple - the Shogunate would cede all its lands to the Uesugi. A humiliating defeat, especially to an opponent who had no where near the numbers of men the Shogun rallied to his banner.
There was no other option for the Shogun, but to commit ritual suicide. Uesugi Noritada, Daimyo of the Uesugi lands and clan, had volunteered to be the man to hold the sword above his head, and grant him that last honor during the rite of seppuku, as the Emperor looked on. As soon as the inking was finished, seppuku was performed, and the Shogun's lifeless corpse was bleeding on the tatami mats of the throneroom. Kneeling in the blood of his former enemy, Noritada was granted the title of Shogun by the Emperor, performing one of the most miraculous rises to power in Japanese history. It had taken 21 years of nearly endless warfare, bloodshed, and luck, but his ambition was granted. From now on, the Uesugi clan would be the rulers of the Japanese Isles. Every daimyo was forced to kneel before their new ruler, and the Uesugi Shogunate was now the undisputed ruler of all of Japan.
A new era had begun. And it would be just as bloody as the last.