People don’t realize that the Japanese legal system is very different than ours. When you are arrested in Japan you are assumed guilty and they will put all sorts of pressure on you to admit that guilt. Also, like the US, the prosecutors/Judges would consider it a grave loss of face to lose so the deck is very much stacked against you so most just plead guilty. Actually the more I think about it the more I think that the US and Japanese systems are the same after all.
I started to read your post and was all ready to write your wrong but you saved yourself at the end.