Japan Travel Fixes
Is it true escalator standing sides differ by region?
The custom that spread is standing on the left in Tokyo and the right in Osaka, leaving the other side clear for walkers. That said, more municipalities and rail companies are now actively discouraging walking on escalators altogether and asking everyone to just stand still.
Officially, leaving one side clear isn't recommended at all, for safety reasons — some prefectures (like Saitama) have ordinances explicitly banning walking on escalators.
If you're unsure, the safest move is simply to match whatever the people around you are doing.