Choosing between Southern France and Japan in October

Having a honeymoon in early October and my partner and I can’t decide… Japan or Southern France + Italy. Budget is around 8-10k (including flights). Both seem like such amazing destinations! We’ll be there for 15 days (with travel days).

Southern France would provide nice weather, plentiful shopping and amazing food, but Japan would too! I’m unsure what Tokyo weather is like in October though.

If we did France + a few days in Italy by train, I feel like that would be a good amount of things to do and explore.

Japan almost feels like it needs as much time as could be thrown at it and that’s the only thing putting me off from being 100% certain about going there. I’d also probably want some time to learn some phrases and learn some characters so I could better navigate for the two of us. I do speak some French but the language thing is not a big deal breaker.

Just looking for second opinions and advice.

Thanks!