"Castle of Temptation" was created 86 years after the peaceful treatment between fiends and humans. It's for the newbies trying to be adventurers, a test for their abilities and strenghts. Since the war is over, adventurers do social and cultural exchanges too, so the castle was created to improve their will and reaction times. Since being an adventurer is a really rewarding job and it gives multiple bonus, this is a test for them.
You are playing as a male boy trying to defeat the succubus queen. In order to do that you have to get there first... Are you up for the challenge?