I’m with @Jeruba in wondering what prompted this Q.
I googled a little and it appears to me that giraffes are not found wild in Japan, but they are in zoos. I could be wrong, but when I look up fauna in Japan giraffes aren’t mentioned. On the giraffe Wikipedia page only Africa is mentioned.
I have a feeling giraffes are few and far between in Japan. Remember Japan is mini small and islands. I assume the natural flora and fauna there is fairly unique, except for what has been brought in, or what they have exported and has become known in other parts of the world because of it.