Can someone go to prison without it becoming public knowledge?
Furthermore, can a criminal case ever be handled confidentially without news of their arrest being made public under a plea of guilt? I'm writing a story where a character, who committed multiple crimes including first-degree manslaughter in his teenage years, turns himself in at the age of 18. The setting of the story is Tokyo, Japan, present day, and the catch is that he was presumed dead until he pledged guilty. I'm wondering if there's a believable way for news of his arrest, conviction and sentence to remain strictly confidential instead of being made public (so that nobody else in the story is made aware that he's indeed alive until later on). I should also mention that the character used to be a public figure and the crimes he committed were crimes against the country in the form of a string of serial murders, but he was working as a hit man under someone else's thumb. If it helps, the story includes a Supernatural element, and the crimes the character committed took place in this "other-world," which could very well be a closely guarded Government secret. I'm wondering if my character could ask that his record be sealed as a condition for his guilty plea, or if, due to the highly sensitive subject matter surrounding the entire case, the government would want to keep the details strictly under wraps. That said, the character's crimes are severe, and considering they affect Japan as a whole in the story, I'm not certain if there's any realistic way I can write his sentencing off as something that's kept on the hush-hush? In simpler terms, I wanted to write this in a way that the character continues to remain presumed dead to those outside of the legal sphere that deal with his direct arrest.
I've been trying to look this up and coming up short. I've looked up various variations of this question on google ranging from "can a prisoner forgo a trial" to "can a prisoner request a private court case?" to "how plea bargains get made". I've looked at the article "Is a Plea Bargain Public Record?" on FindLaw.com and the general specifics of the Japanese Judicial System on japan.kantei.go.jp. I even tried looking up "the nature of court cases that are closed off to the public" and "exceptions to the rule that states most legal proceedings should be public." I might be failing to word my questions correctly, but they feel very hyper-specific and difficult to pin down, which is why I couldn't find any exact answers to my question through research.
I really hope someone has an answer! Thank you.