He used ropes, and he had to learn how to do complicated knots to keep the criminals from escaping. Japanese bondage started when a police officer from a long time ago needed to tie up criminals that he was arresting. That is why when it comes to making Bondage/Discipline, Dominance/Submission, and Sadism/Masochism, or BDSM for short, they seem to do it like the real experts that they are.
And why not? They have the world's biggest porn industry. When it comes to making porn films, the Japanese are one of the best at doing it.
