A journalist is supposed to observe and report his story, not become part of it. But by the time Jake Adelstein found himself face to face with an enforcer for one of Japan’s most vicious mafia gangs, it was too late.

“Erase the story or be erased,” was the yakuza’s message. “Your family, too.”

It was an offer Adelstein couldn’t refuse. As a Tokyo crime reporter for the Yomiuri Shinbun, Adelstein’s tirelessness and loyalty had won him respect and trust on both sides of the law as well as at Japan’s largest newspaper. But when an organized crime boss threatens to kill you and your family, it’s time to go, Adelstein reasoned.

He packed up and left Japan with his story. It was a fantastic one, too. Yakuza heavyweight Tadamasa Goto had sold out his own gang to the FBI in order to receive a liver transplant in the U.S. ahead of ailing American citizens. But as juicy as the story was, it wasn’t worth dying over.

That changed when Goto came after Adelstein again, putting the two quite literally in a fight to the death. Writing his story could get Adelstein killed, but it was the only weapon he had that could stop Goto.

Adelstein’s showdown with Goto is the climax of “Tokyo Vice: An American Reporter on the Police Beat in Japan” (Pantheon Books, $26), but the former Yomiuri reporter goes further, pulling the curtain back on a sordid element of Japanese society that few Westerners ever see. In addition to his clash with the yakuza boss, Adelstein details the more notable cases from his 12-year career at the Yomiuri, including “The Chichibu Snack-mama Murder Case” and “The Emperor of Loan Sharks.”

“Tokyo Vice” lingers on the yakuza, with good reason. Japanese crime gangs are much more powerful than their American counterparts because Japan lacks the racketeering laws and many other legal weapons police use to combat organized crime in the U.S. The yakuza has its hooks in nearly every aspect of Japanese society, and spreads its influence through vast networks of legal front companies, Adelstein says. Because Japanese law regards the yakuza gangs themselves as legal entities, the yakuza is expert at hiding in plain sight.

It’s a state of affairs that gives Adelstein all the more reason to fear Goto and ultimately, all the more reason to tell his gripping story.