Yuya Motomura, a mahjong parlor manager in Japan, had always wanted a way to prove himself to a society he felt looked down on him. Then Russia invaded Ukraine.

The 45-year-old is one of a handful of Japanese men who have joined Ukrainians battling the Russian invasion, defying their government's warnings and bucking a decadeslong national principle of pacifism.

Japan's military is constitutionally limited to defense and has not fought since World War II.