Best way to get a French bulldog from Kansai to Hokkaido

I’m gonna be going back to my country for at least a year, and French bulldogs can’t fly until November from what I’ve found (if anyone knows an airline that allows it let me know).

My plan right now is to leave my dog with a friend in Otaru, Hokkaido now and then coming back at the end of October to spend some time with family and bring him back with me.

I was hoping to be able to fly out of Sapporo after dropping him off. Can’t leave my car there, unless there’s some dedicated multi month storage that I don’t know about.

There are one way rental car agencies but from what I’ve found they exclude Hokkaido bc they don’t want to pay the ferry back.

Small dogs can ride Shinkansen but there’s a 10kg limit. My dog isn’t big but he’s a dense little ball of muscle. Are they actually going to check the weight?

Any other ways to do this that I’m overlooking?

Thanks 🙏