I wouldn't worry about this at all.

When I start worrying about is when it is FC AC JC ... WC ... YC

Based on what you are seeing, more likely it's pretty full down the back rather than up the front, although it's probably pretty busy up the front too.

Anyway lots of options for TYO, I don't think you should be concerned even in the worst case of being bumped off the flight (extremely unlikely).