Plot idea: Demon Conquest Fantasy (seeds of chaos

The kingdom is at peace after 5 years of the war of Demons vs humans. The humans have won, becoming the race that controls everything and divided the kingdom into six places of ruling. the main hero who won the war and lead the humans to victory began to live a quiet life with his loving wife. little did he know the smaller races (orcs, elves, dwarves, goblins, etc) were not treated fairly in the kingdoms. But after he goes to work, he comes home to find his wife was taken and is told by twin demons to meet him at a castle months away. the demons dont hurt the wife, they treat her well and feed her and dress her, but she cant leave the castle. the human hero realizes that the twin demons are the children of the last demon ruler, and force his hand to help them take back the kingdom