As far as I know there is islam in Japan, just not as massive as in other places in the world and the country has policies that disencourage muslims from thinking of Japan either for staying there or work.
Muslims constitute less than 0.1% of the Japanese population. And those Muslims are primarily Malays, Indonesians, and other SE Asian types.
There are virtually no Halal eateries in Japan, nor are there visible Mosques.
In light of this, people saying "but... but... there
are Muslims in Japan" are totally fucking retarded. The very few Muslims that live in Japan keep their heads down, for fear of being deported. Most of them work in menial labor, besides.
France is 10% Muslim, is going full-Halal, and Mosques are everywhere. Big difference.