Tenshō-Jingo

Tenshō-Jingo (甲斐国, Kai-no-kuni) was the province of the Takeda and home of Ueda Castle. After the Takeda's demise, the place became a very contentious area until Masayuki Sanada was able to claim the area for himself, after allying and double crossing many clans before surrendering to the Toyotomi to prevent any more threats.

Role in games
In Samurai Warriors 3 the battle is called Kai Province in non-japanese versions, the H​ōjō attempt to fight off a Sanada-Tokugawa coalition in Lady Kai's second stage. She starts off by repelling the Sanada forces rather easily, before being forced to deal with the defection of Yoshimasa Kiso. Then the Tokugawa take a large offensive to Ujiyasu causing Kai to have to defend her lord and open the Tokugawa encampment from it's exposed behind. Despite the Hōjō's success here however, the vacuum left in the wake of the struggles still allows the Sanada to seize power.

In Samurai Warriors 4-II, the Tenshō-Jingo Conflict is a new map and represents the struggles of Kai province. In Naomasa's story, the Tokugawa and Uesugi ally to fight the Sanada and Hōjō. Naomasa breaks through the Tsutsujigasaki manor and fights off the Hōjō support, isolating the Sanada in the corners. The Tokugawa seize the keep but it's rendered worthless after all the damage incurred by the battle. The Uesugi also get their perspective shown but the outcome remains the same.

In Samurai Warriors: Spirit of Sanada, offers a more in depth look to Masayuki's machinations during chapter 6 and 7. In this time, the Sanada ally and betray the Tokugawa, Uesugi and Hōjō throughout several battles while seizing Numata Castle for themselves. Once Masayuki establishes his own land, he shrewdly surrenders to the Toyotomi. The outcome of these chaotic events inspires him to splinter his clan with Yukimura remaining loyal while Nobuyuki is sent to the Tokugawa when Sekigahara comes so his lineage can survive no who wins.

In Nobunaga's Ambition, Kai Province was designated as an important territory of Shingen and Katsuyori along with Shinano Province.

Historical information
The Tenshō-Jingo conflict is a collection of battles and posturing between the Hōjō, Uesugi, and Tokugawa after the death of Oda Nobunaga. The campaign began with the Hōjō driving out the demoralized Oda forces under Takigawa Kazumasu. The Hōjō managed to capture Komoro castle, placing it under Daidoji Masashige. They pushed further into Kai, capturing and rebuilding Misaka Castle as they squared off against Ieyasu, who had made inroads by absorbing former Takeda officers into his army.

During this time, Kagekatsu finally broke free from conflict with Shibata Katsuie and began looking south towards Ueno and Shinano province. The Uesugi leader offered aid to Ogasawara Dosetsusai to establish a foothold into the former Takeda forces. Kiso Yoshimasa, a recent ally of the Hōjō, tried to stop their advance, but was too slow in his efforts. This progress pushed them close to Kawanakajima, adding pressure to the three-way tug of war.

Eventually the Hōjō and Uesugi began skirmishing with each other, with the Hōjō gaining the upper hand through the added strength of the local warlords like the Sanada, who had initially sided with the Uesugi. However, this focus on the Uesugi cost the Hōjō time needed to check the encroaching Tokugawa. Not wanting to be pinched between the two clans, Hōjō sought peace with the Uesugi, yielding the northern-most counties to gain this peace.

Next the Hōjō and Tokugawa prepared to fight, with tens of thousands of Hōjō forces beginning to siege down the castles under Ieyasu's command. Even skilled commanders like Sakai Tadatsugu were unable to fight against such overwhelming numbers. However, as the Hōjō pushed forward and stretched out their forces, they were defeated at the battle of Kurokoma. This defeat led to the recently submitted minor lords like Yoda Nobushige to swap loyalties to the Tokugawa.

Sanada Masayuki swapped sides once more, seizing Numada castle and submitting to the Tokugawa. They also pushed the Hōjō at Komoro, requiring Hōjō Ujimasa to commit more forces to the effort. Within a month, however, both Ieyasu and Ujimasa had external forces threatening their far boarders. These external threats led the two to make peace and end their conflict. Around the same time, the Sanada betrayed the Tokugawa and submitted to Hashiba Hideyoshi as an independent daimyo.