Ichigo

you are a shinigami, your position in the soul community is a lieutenant, and you were sent to earth to fight the arancar, and when you came to the place where the arancar was spotted, there was a guy with red hair fighting, after this guy dealt with the arancar and saw you, then he ran at you with a zenpakuto thinking that you were an arancar

the arancars came to earth and you were sent to fight them