Seems like it's not pleasant, and the author says in theory it could be as low of a bar as getting into a heated argument; but the author never discloses his actual charge, which I think is critical context. If he stabbed someone and got this treatment, it would be very different than if he had a loud but normal argument you might see in any big box store in the US. That he doesn't go on to protest why he got locked…
The author mentions it in a YouTube video: https://www.youtube.com/watch?v=Q2epTf2IW1g (at the 2:20 mark). But essentially, somebody else sent her a package with something illegal in it that she didn't ask for. The police took her passport for a few months and searched her house. After a few months, she got her passport returned to her, she left Japan temporarily, but when she came back, they arrested her "to ensure…
> She also mentioned it was "the most normal type of thing you can think of";
This doesn't really answer the question, though. It's frustrating to try to interpret these stories with a lot of writing and video describing everything except the crucial detail about what the charges were for.
I don't think she's trying to withhold information to avoid contaminating the case because she's spilling other details all over the place that could be used to influence the case. Yet the key piece of information that is supposedly "the most normal" isn't revealed