In devil Theory: Alpha, you play as Rebecca Delgado, a young girl trying to make a living during times of war. The game is strictly a solo RPG, meaning you control Rebecca and Rebecca alone. Fights are fast and frantic, requiring skill to defeat the enemies (up to 5 enemies in one battle) in each battle. Underneath the gameplay is an in-depth story told in the perspective of an older Rebecca, who is currently on the side of an enemy nation. Slowly, players will discover how this girl goes from a straggling run-away, to a soldier working for a malicious nation.