It seems, according to the press reports nowadays, that Sakai Noriko or NPi the fallen Idol has been directed by Ex-lawyer(75 years-old) who was smashed out from the legal profession because of his notorious malpractice against laws. And, he knows the law and how to run from the law and how to avoid the sentences from the court.
So, Sakai Noriko was, according to his professional advice, staying in some places(especially hot spring areas) to get rid of her drugs from her body, and then, after the suitable time when the urine has no evidence of the drug, she surrendered herself after hair cut to avoid DNA test.
This ex-lawyer knows that confession and DNA test ( indirect evidence) could not be enough for prosectution legally.
Anyway, NPi's father, who is dead already, was a boss of one of the Japanese mafia clan.
This black-masked underground "lawyer" shall be tested and revealed under the sun duely.