A white whale-like humanoid cryptid living near Antarctica and New Zealand.
The ningen was spotted by japanese fishers.
Maybe an unknown pentadactyl tetrapod. Perhaps a mammal.
We know, that this creature was spotted by japanese "whale research" boates.
Of, course, it would be possible, that they were whalers and not really researchers.
In the japanese mythology exists lots of spirits for nearly everything... Bakabake-san, Karakasa-obake, Chochin-obake...
So... what about giant humanoid whale spirits, which want to say:"Stop whaling, idiots!!!"
Yeah... why not?