Rance IV: The Legacy of the Sect

Original game manual can be found here. (japanese only)

This game was translated into English on 09/03/2013 and the link to download can be found on the translator page.

Summary
After the events of Rance 3, Rance and Sill find themselves on a floating island of Ylapu where they have to deal with Helman force and stop the awakening of an ancient super weapon from the lost times.