i have found that most escort agencies that specifically list or focus on Japanese escorts in london are fake and/or scams.
do you guys know of any that are actually good/reliable?

Same, Most of the oriental escorts I've been with have looked nothing like the photo on arrival. I've walked from so many I've stopped waisting my time with them 

Miss69 or Olina are the best choice when it come to Asian escorts. But i'm not sure if they have Japanese escorts at all.