[Because imagining what happens after Sekigahara is fun. For this one, I’m snagging lots of things from the Sekigahara part of Ieyasu’s Wikipedia article. Clothes designed based on this portrait of him. Will design armor version later OvO„]
Having defeated Mitsunari during the Sekigahara Campaign, Ieyasu had set out to hunt down many of the other samurai and nobles from the side of the Western Army, in order to unify the lands and establish power.
He gained the title of Seii Taishogun after succeeding, becoming the ruler of Japan and setting up the Tokugawa Shogunate, finally achieving the peace that he had always dreamt of.
Having worked so hard for it, and for having been forced to kill so many people including his close friend Mitsunari and his rival Sanada Yukimura, Ieyasu swore that he would make sure this peace stays, to make up for everything.
But even then, he was always haunted by the past and felt guilty, making him always tense and too careful, afraid of breaking his oath. Soon he was paranoid enough to attack even his own allies the moment there was the slightest report of a suspicious movement. Despite the war having ended, more lords were killed in the name of safety precautions.
Ieyasu’s vassals were scared of what would happen in future. But no one daring enough to start a rebellion for fear of its effects, they decided to turn to the Date for help, Masamune being good friends with Ieyasu after fighting together in Sekigahara.
- By this time, Ieyasu was close enough to Masamune to call him by his name instead of his title.
- But he always refused to listen when Masamune told him to stop his attacks on the other clans. So the latter decided to try find some other way around it.