Last Rebellion is set in the world of Junovald, where death is not a natural process and monsters roam free after dying. The only way to put a soul to rest is with the power of a Sealer. Sealers are accompanied by Blades, skilled warriors who can be revived eternally. After a new weapon is delivered to a remote kingdom to deal with its monster problem, the king and his eldest son are slain, and the weapon stolen.
Players control Nine, a Blade, and Aisha, a Sealer, as they travel through many linear levels, searching for the killer of Nine's brother. The two protagonists share a single body, allowing them to share stats and an HP bar. However, spells must be equipped on either Nine or Aisha, depending on the situation. Combat is fast-paced, with multiple body parts of monsters that can be targeted with physical attacks, creating combo chains and increasing damage.
In combat, hitting enemies in a specific order can create a chain reaction, applying more "stamps" to body parts and increasing magic damage. Once an enemy falls, it can either be poached for MP by Nine or killed for good by Aisha. As players progress through the game, they will uncover the truth behind the king's death and the fate of the kingdom.