Depending on the game by Valkyria.

Dragundaala, a nation belonging to the descendants of dragons, continues to be conquered by a military of demons. Together with the king and queen captured through the demon army general, Ginyol, princess Catue tries to rescue them, but gets caught. Stop worrying, however, as Ginyol agrees to free the king and queen, and withdraw his army entirely if princess Catue can endure his sexual acts of depravity for 7 days.