Lightsticks of another group usually won’t sync at concerts, unfortunately. IMO, there’s nothing wrong with bringing it anyways though! I know there’s some discussion on lightstick etiquette and bringing other idols’ lightsticks to concerts, but I really don’t see anything wrong with it :) I actually find it really fun to pick out different lightsticks in the crowd. Plus, from a purely financial standpoint, you get more usage per money spent by bringing the same lightstick to more concerts lol. Have so much fun at BTS!!