6 month Asia backpacking itinerary help

Hi all, I'm currently planning a ~6 month overland route through Asia starting January 2027. I'm planning to fly to Sri Lanka and complete the remainder of the route without flying. However, I'm conscious of both not over rushing and hopefully avoiding some regional weather patterns (e.g. monsoons on India, rainy and hot summers in Japan).

Please can I have a critique of my 6 month general plan beginning January next year, and whether this seems realistic or overambitious? No set itinerary yet but I'm keen on all things hiking, cultural, and eating!

Budget is flexible, though I'll likely be staying in private room hostels throughout. Any country specific tips would be appreciated as I continue planning!

Sri Lanka - 2.5 weeks (from 1st January)

India - 8 weeks (general South to North route)

Nepal - 2.5 weeks (arriving mid march for trekking season)

China - 6 weeks

South Korea - 2.5 weeks

Japan - 4 weeks (I believe I'll get to Japan by June, which I understand is the start of the rainy/summery season)

Thanks!