For 12 years, Jake Adelstein was embroiled in the seedy underbelly of Tokyo crime and nightlife, spending late nights schmoozing with police, conducting investigations at brothels and fielding death threats from the Japanese mafia. Adelstein himself, however, was not in law enforcement or a criminal. Rather, from 1993 to 2005, Adelstein worked as a crime reporter for the Yomiuri Shimbun, Japan’s biggest newspaper, the only American to hold such a role.

Adelstein has chronicled his alternately chilling and hilarious story in a new book, “Tokyo Vice.” He discussed the book and his singular career at an event at the University of San Francisco on Oct. 21.

Adelstein went to Japan in 1988 as an exchange student on a quest for “spiritual enlightenment,” studying at Sophia University and living in a temple, he said. After graduating, he applied to become a reporter for the Yomiuri Shimbun, a competitive process involving a test and interviews, with thousands of candidates competing for dozens of jobs. He was selected and assigned to cover the police beat and eventually to an even grittier role: covering the yakuza, a complex network of several different branches with about 86,000 members across the country, according to Adelstein.

The relationship with the police and the yakuza is a complicated one, allowing them to function as an open secret. The Japanese public as well has a seemingly strange perception of organized crime, Adelstein said, with “most Japanese regarding them as a second police force that keeps Japan safe.”

Like much of Japanese culture, Adelstein said developing sources as a reporter is conducted through a system of reciprocity, giving and receiving favors. He visited the house of a potential source, for example, but was turned away, his request for an interview rejected. Adelstein had come with ice cream, however, and the source begrudgingly invited him to share the sweets with his family, eventually relenting to an interview.

Being the only American reporter covering the yakuza “was more of an asset than a liability,” Adelstein said, because it allowed him to connect more easily with people and made him “memorable.” Adelstein attained widespread notoriety for breaking the story of how a major gang leader arranged a liver transplant in UCLA, a scoop that proved dangerous. After breaking the story, he said he was called to a meeting with yakuza members, told that if he didn’t come, he would be killed. He was then put under the protection of a rival organized crime group, a testament to the complicated moral codes and conflicts between the gangs. Now Adelstein has police protection and a bodyguard in Japan, a former yakuza boss himself, “so I feel slightly safer,” he said.

In 2006, Adelstein became the chief investigator for a State Department study of human trafficking in Japan and now serves as the public relations director for the Polaris Project Japan, which combats exploitation of women in the sex trade. He grew passionate about the issue when he reported on sexual slavery in Tokyo and became frustrated with the refusal of the police to prosecute offenders. There were no laws against human trafficking, no shelters for victims and little understanding of the issue. While the situation of foreign women in the sex trade is gradually improving, Adelstein said, his organization increasingly assists a new set of victims: underage girls who became prostitutes for pocket money and find themselves blackmailed into sexual slavery.

The Asia Society, Japan Society of Northern California and the University of San Francisco’s Center for the Pacific Rim sponsored Adelstein’s talk.