Demons, brother, mother and two cities

I was part of an elite group eliminating demons in a city. Once done, I saw my brother at the border. We entered the new city together to find out Mum who was spending some time in the new city. The locals told me their city didn't have demons but had some other mysterious foe. As we entered the market, I saw my Mum climbing stairs to enter a place. I called her and she looked around but didn't see me. I faced my brother and said it could be the foes that have done this. Then we started climbing the stars to reach her.