A man called James was born with a interesting ability. He have the power to completely and permanently wipe out the effects of demonic energy. It isn't a talent he could control however, it work passively. If he touched a monster girl, she would permanently turn into a regular human woman. Slimes, Arachnes, Lamias, even the strongest monster girls such as Pharaohs, Baphomet and Lilims were turned human. The victims also became immune to demonic energy, all monster girls who tried to reverse the transformation failed. James's power also work on incubus and regular humans. Incubus were turn back into regular men and the already normal humans who touched him became immune to demonic energy.
It wasn't something he deliberately do but he just run into situations where touching people, whatever accidentally or intentionally, was bound to happen. Yes, he did ran into many such situations, he possess a amazing ability and people took notice. Particularly after people discoved that the effects of his power are permanent. Many people, particularly the former monster girls, tried to get rid of their demonic energy immunity but to no avail. The most intelligent people of the world tried to create a cure but it's impossible. Even the Demon Lord and Gods are completely incapable of creating one. James's power is beyond everything and anything, nothing can stop it, nothing can reverse its effects. Even the knowledge and technology of the people from the Other World, a world where there's only humans, no monster girls and magic, are useless.
James became a target. Some people wanted to exploit him or make experiments on him, he was seen as a threat by some and as the key to humanity's salvation by others. However, James just wanted to be alone. To avoid being captured or even killed, James became a nomad, moving from villages to villages, cities to cities, constantly moving and traveling. He is always on the run. This time, he's running in your city. Yes, your city, where you live. Â
You're just a regular man, married to a monster girl. One day, you decided to accompany your wife for shopping in the market. Things were pretty calm until you see a hooded man running through the crowd, almost bumping people. He is being chased by guards and as he run past you, he accidently bumped your wife, touching her. Your girlfriend loses balance and fall to the ground as the hooded man and the guards moved to another part of the city. You give your hand to your wife and as she tried to took it, something happened. Her whole body become shiny, she's covered with lights but they eventually go off. Your girlfriend has changed, she's no longer a monster girl, never will be ever again. There's nothing you can do to reverse the transformation, even the smartest minds, Demon Lord, Gods and the Other World can't help you. No magic or technology, whatever how powerful and advanced, can transform back your wife into what she was. Â
What do you do?