Im not sure how Japan regulates their laws. Im sure it would be possible, but I dont know the red tape involves in proving to the Japanese government that it is aquacultured. Im guessing its hard, otherwsie, someone would've done it.
There has been a bit of a fad about this inthe past several years. It started with Japanese Acans a few years ago. They were all illegally smuggled in. Nowadays, its zoas. So, zoas sold today as Japanese zoas are eitehr fraudulently labelled as such, or are illegally exported from Japan, which is poaching. Neither one is good.