Unveiling the Unknown

This is a visual novel with an unusual plot twist that you may not see it coming. The main character is pretty normal and doesn't have any special skills. However, he will have to take the place of his twin brother. These are really big shoes to fill because unlike him, his brother is a skilled warrior. He fights and defeats demons. He is basically a legendary hero of the city. There's more to it. The main hero of the game is enchanted and cursed by an evil demon queen. All the time, she constantly plunges him into extreme erection making him always ache for some release. The only way to stop the magic is to find someone to fuck.