It's always a misnomer to call Japan the first victim of nuclear weapons. They should be more precises and say fission weapons.
No one has yet been a victim of fusion weapons. The scale of damage is 100 to 1000 times larger. If a 5 megaton fusion bomb was dropped on Hiroshima instead of a puny 20 kiloton fission bomb the damages would not have been localized to just Hiroshima--but nearby cities as well.
Although if you want to get critically correct the fusion bomb is both fusion and fission. Fission is used to trigger the fusion chain reactions.
Which is why is one reason why it's so devilishly hard to get fusion to work commercially the immense temperatures and constraints required to sustain the chain reactions.
So far fusion has just been fizzling but were getting closer.