Kasai-Ōsaki Uprising

The Kasai-Ōsaki Uprising (葛西大崎一揆, Kasai Ōsaki Ikki) was a series of riots raised in protest by former Date retainers against Yoshikyo Kimura. The lands were previously Date territory but given control to a new lord as punishment due to Masamune's hesitation to support Hidyoshi's siege at Odawara Castle. Harsh taxes and general public discontent escalated into a various outbreaks of violence until it is under Date rule again.

Masamune allegedly secretly supported the uprising by sending firearms to rebel forces. However, the letter implicating his involvement is disputed by some historians to be have been forged and created as propaganda.

Role in Games
The stage makes its first appearance in Samurai Warriors 3 with Masamune leading the uprising himself. In his version of the stage, players need to defeat Hideie Ukita and Yoshitsugu Ōtani to open the southeastern garrison to allow rebel forces to advance. Kotarō will appear with doubles to advance on Masamune's position and Kunoichi will appear to remove Magoroku Saika from the field. Yukimura, Mitsunari and various other reinforcements arrive in staggered waves at the south to help Kai once Kunoichi is defeated. Players are advised to head to the top and defeat Kai to end the battle before enemy reinforcements overwhelm their own forces.

In Kai's story, Akihisa Kashiyama, Akanaga Kashiyama, and Shigenobu Muyari begin the battle by attacking the Toyotomi main camp. Her father is surrounded by rebel forces led by Harunobu Kasai and Yoshitaka Osaki; the rebel leaders must be defeated before Ujinaga's health is reduced to half. Kunoichi and Kotaro arrive as allied reinforcements. Once Ujinaga is rescued, a mission to escort him to meet his brother Nagachika is triggered. After Yukimura arrives and defeats Magoichi, the rebel main camp gates open and allow players to defeat Masamune to end the battle.