Japan has an insanely hight conviction rate in pretty much all crimes.
What happens is this: police find someone who is plausibly guilty (very low threshold and lots of bias) and keep them in custody for a long time (sometimes months) until they finally confess. Case solved.
So what you have just described is just business as usual for Japan.
(I forgot about this part in my original post, for thanks for being the impetus for making me remember :P)
Most crimes in Japan have conviction rates of well over 90% for the reasons I wrote so I would be very surprised if this case was any different.
As an aside, my wife is Japanese (born and raised there) and in her mind, once the police or the authorities say something, it's God's Truth.
It doesn't help that in Japan, the Emperor is believed to be descended from the Gods.
I'm breaking her of that concept, because, let's face it, man is fallible, but it's been an interesting struggle.
At first, the Japanese police "interrogated" four of the people whose computers had been hijacked. THREE OF THEM CONFESSED. The only reason they're not behind bars now is because:
1. Even the Japanese police noticed that there was something wrong with the case. It didn't make sense that these four people were co-operating.
2. The fourth guy was savvy enough to figure out what had happened, and explain it to the police.
This kind of crap goes on all the time here. Japan is what is known as a "soft police state".
The flip-side is, the police are so dependent on the confession to secure a conviction that, and so inept at other forms of investigation, that if you have the means to resist the pressure to confess, you walk free. That's part of how the yakuza (criminal gangs) survive in this highly regulated society.