Well that was certainly......interesting

My favorite part was where it said ".....while no solid evidence of Ningens' existence has been found...blah blah blah"
More unconfirmed eyewitness accounts of creatures that seem pretty unlikely to me, that there is no biological reason for. Look at the shape of most swimming creatures. Torpedo like...lacking floppy humanoid appendages. Now I'm not an evolutionary biologist and I honestly hate invoking the "E" word anywhere around here - lest Harsh_Patel come by and jack the thread. At any rate....there is just no reason for creatures living in the ocean open, looking like those. They'd die out because of their inefficient design.
And hell, I'll go out on a limb on the other side of the tree and say why would God - in his/her almighty wisdom create wierd people-looking creatures and stick them out in the ocean where nobody but drunk Japanese fishermen would ever see them? I just don't buy it. The website can say that the Japanese government is covering the whole thing up - because hey, when governments cover things up, the whole point is that there isn't any evidence. You can claim any ridonkulous thing you want and claim the government is covering it up and then pat yourself on the back because you don't have to prove it. Fringies will flock to your door and Buy your book!
Anyway..my vote - highly unlikely.....almost as much as Hellboy.