Kougai Koufuku

Visual Novel Version
A general and a new character in the sequel, Shin Koihime Musō. A cunning warrior who infiltrates Sōsō's forces on a pretense of defection during a major naval battle (based on the Chi Bi's Battle) and sets the Gi faction's ships on fire. If Kazuto joins the Gi Faction, Kōgai is eventually killed for these actions.

(Source: Wikipedia)