If you mean Shirakawago, then gasshou house village near Takayama, then your itinerary is not a good one. The detour to go there and back takes too much time unless you also have time for Kanazawa and/or Takayama.

If you want further itinerary help, it's best to list where you intend to be on what day.

Yes, I think this itinerary not a good one too.

I now changed to the following

Tokyo - Takayama - Shirakawa

I now hesitate to go further up to Toyama or Kanazawa ?? any idea ? any bus from there to Tokyo ?

or should I leave Shirakawa and take the direct bus to Nagoya ??

any advise ?

How many days? When (month/season)? Where are you departing from at the end of your trip?

Bus from Shinjuku to Takayama. https://www.nouhibus.co.jp/highwaybus/shinjuku_en/#timetable

Bus from Takayama to Shirakawago to Kanazawa. https://www.nouhibus.co.jp/highwaybus/kanazawa_en/

Shinkansen is the easiest and fastest to get from Kanazawa back to Tokyo.

Why do you want to go by bus to Nagoya? The train (Limited Express Hida) is faster and easier.

https://world.jorudan.co.jp/mln/en/?sub_lang=nosub

I think no point travel down to Nagoya.

I will continue my trip with kanazawa and Toyama and then last stop Nagayo and take shinkasen back tokyo.