Siege of Osaka: A series of battles undertaken by the Japanese Tokugawa shogunate against the Toyotomi clan, and ending in that clan's destruction. Wikipedia: Siege of Osaka

Sakamoto Ryouma: From the Bakumutsu period, Oryou's nickname comes from his wife, Narasaki Ryō. Wikipedia: Sakamoto Ryouma

Tokugawa Ieyasu: Was the founder and first shōgun of the Tokugawa Shogunate of Japan. Wikipedia: Tokugawa Ieyasu

Sanada Yukimura: Especially known as the leading general on the defending side of the Siege of Osaka, Saemonza's nickname comes from him. Wikipedia: Sanada Yukimura