World: Bad World where things are bad and king and people are bad and selfish and want to use the summoned person as just tool to make their own life easy and they put the enslavement collar on the person who they summon so they can use them as they please and have fun while you can't to your world back and they want to use you to increase their power as the person who come from another world get ability to absorb the the strength of the person they kill and possess special powers from this