This game is not part of the official Rance universe timeline, forking off after the events of Rance 4.2, as a "What if" episode.
The prelude starts with Rance leading a band of bandits in rural Helman Empire. The Imperial Patrol crushed his band with overwhelming force, and captured his slave, Sill. Rance fled to the borders of Leazas where he was rescued by Kanami, personal ninja of Lia, queen of Leazas.
Eager to take revenge upon Helman and rescue his slave Sill, Rance agreed to marry Lia. As the new king of of Leazas, Rance set his first step on a path that eventually leads to world domination, or death.