I think it might have been a manga, protagonist is demon lord subordinate, the demon lord had cast magic on all his subordinates to force them to obey him. The hero didn’t know they were forced to obey. That’s basically the intro to the story
Sounds a bit like "I Reincarnated For Nothing" by toika. It may not be the one you mean since the mc changes from a subordinate to a hero but it does fit the bill
The mind controlling collar being a focus does sound a lot like I Reincarnated For Nothing. I thought of Yuusha Party no Kawaii first because of the subordinate to demon lord, but I don't remember any mind controlling collars.