Yeah, Japanese prisons are actually horrible. You basically have zero leeway in anything you do. You’re basically expected to sit quietly in your cell for 20 hours of the day. The rest of your time is spent either quietly eating, or kneeling quietly in the yard during your mandated outdoor time. Punishments for non-conformity are strict and swift, and guards aren’t afraid to beat you senseless for speaking out of turn.
Japan is actually extremely conservative, and that really shows in their justice system. They have a near 100% conviction rate after someone is arrested, because there are basically zero protections for the accused. No right to a defense lawyer, prosecution can exclude exculpatory evidence, police can drug and beat you to force a confession, etc… Only 0.2% of accused people are actually found innocent. And no, I didn’t mean 2%. I mean 99.8% of arrests lead to a conviction.
They have a large amount of tolerance for socially “normal” crimes like public intoxication, (the stereotype of the drunken Japanese businessman stumbling home at 2AM is very real,) but if it’s a socially unacceptable crime (like petty theft) or if you’re a foreigner, then they’ll throw the book (and basically the entire library) at you. The Yakuza is basically allowed to operate openly, as long as they don’t bother the normal citizens. But if you’re accused of smoking weed, you can expect to die in prison.