Hi Alexandra, I just saw this post and thought ooh, she comes to Japan today! Hope you’re enjoying it so far!
I’m not sure what you man by pop up character cafes, but there are plenty of specialty cafes in the Tokyo area especially Akihabara. Did you mean like anime characters? Because there’s a bunch of them out right now, if you search your favorite anime in jpninfo.com a cafe will almost definitely come up.
How’s Japan treating you so far? :D