As far as I can think of, about the only European gateways with flights <10hr to TYO would be something like Helsinki or Moscow. But then how are you going to get there? Otherwise just about everywhere else (eg, LHR, AMS) will entail a flight longer than what you'd like.

I would just bite the bullet if I were you. Even from YYZ, we're only talking 3hrs longer than from SEA, YVR or HNL. And you could just drive there from where you live. Once upon a time I used to live not too far from where you are. I've driven to YYZ to take the nonstop to Jpn.