$6 billion in aid to Ukraine from Japan is amazing IMO.
AFAIK Japan is considering beefing up their military a bit like Europe has already decided.
Maybe Europe and Japan could cooperate on research/production/acquisition of weapons a bit like we do now with Canada entering the SAFE agreement. Japan is a very politically stable country much like Canada, and could be an excellent defense partner.
Europe and Japan definitely have common defense interests, and USA becoming an unreliable defense partner must be just as much a problem for Japan as it is for Europe and Canada.