I had a couple alternate ideas,

Follow the Mekong river from China to Vietnam (but I have 700c wheels on my touring bike, so not sure how well I would go if I broke a wheel)

Pull the Japan ride forward, but only ride from Cape Sata - Tokyo (There may be a few days of snow, and I'm not that confident with my bike on icy roads, as I have never cycled in a cold climate before)