While looking a lot like an adult of the more common species Ebinania vermiculata, this specimen was examined and identified as the rare Psychrolutes macrocephalus by the Tokai University. This is the only specimen of its kind known in captivity.
@Mr Gharial Haha, we went there for a reason! Insane species diversity when it comes to fish. I will upload some other animals too. Note: not every species I'm uploading was photographed in Japan, the Rainfordia for example.