Laws You Must Not Break

What are the risks of hanging around an area like Shinjuku's "Toyoko"?
Getting involved with the minors who gather in areas like Shinjuku's "Toyoko," or with illegal touting and prostitution, can get you caught up in serious trouble. Involvement with a minor in particular can be a serious crime even without any money changing hands.
Is it true that drugs legal at home can still be illegal in Japan?
Yes. Cannabis is illegal to possess or use in Japan even where it's legal at home, and tourists have been arrested and deported for it. Some prescription medications — certain ADHD medications and strong painkillers among them — are also restricted or banned depending on their active ingredient.
What should I know about photography and voyeurism laws?
Taking photos up someone's skirt, or secretly photographing someone changing or bathing, is a clear crime under each prefecture's public nuisance prevention ordinance — even first offenses are commonly arrested and prosecuted. Japanese-market phones can't have their camera shutter sound disabled specifically as an anti-voyeurism measure.
What traffic laws apply when riding a bicycle?
Bicycles count as light vehicles under Japan's Road Traffic Act — drunk riding, using your phone while riding, and running red lights are all punishable, same as for cars. A 2023 law revision made helmet use a "best effort" obligation for all cyclists (no penalty for skipping it, but injuries tend to be more serious without one).