Japan must strongly condemn Russia on the UN Security Council this month and lambast the fact they are still on it.
The Hague International Courts are moving on without the UN however and are starting to make moves on Putin and Russia already:
https://www.pravda.com.ua/eng/news/2023/01/4/7383587/
Supporting the idea is one thing.
Now get more Russian assets, funds, bonds and wealth to seize, freeze and transfer to Ukraine to repair their nation and getting Russia to pay for it – doing great so far – but they must be faster.