to capture a heart (Sun x Moon)

for forever and a day demons have hunted humans. but what is humans could fight back? Creator was named such for creating technology to fight them. but creator has a son...
Sun never saw things the same as his dad, thinking that we should make friends with the demons to that the endless fight would end at last... but he is frowned on for this so he keeps it to himself. but when he seemingly becomes the target of a one of the most well known demons he sees it as a way to learn about them! if he doesn't die first...