A 41-year-old Japanese man who used to work at the Hong Kong branch of Credit Suisse was arrested Wednesday for allegedly helping launder profits from a massive loan-sharking operation, Tokyo police said.

The Metropolitan Police Department arrested Atsushi Doden after the former banker turned himself in to police accompanied by a lawyer. He arrived at Narita airport near Tokyo on a flight from Hong Kong earlier in the day.

Police obtained an arrest warrant for Doden last week, and Japanese authorities confiscated his passport to entice him to return to Japan.

According to investigations, Doden and others conspired to set up an account at Credit Suisse’s Hong Kong branch in the name of Susumu Kajiyama, a former senior member of Goryo-kai, an affiliate of the Yamaguchi-gumi crime syndicate. Goryo-kai now goes by the name of Nidaime Mio-gumi.

Police suspect that Kajiyama, the so-called king of loan-sharking, operated an extensive loan-sharking ring whose profits were funneled to Yamaguchi-gumi. The Credit Suisse account was used to launder the money garnered through the illicit business, they said.

Investigators said that Kajiyama and others involved in the operation hid the profits from their loan-sharking ring by purchasing some 4.635 billion yen worth of discount bank debentures, converting them into cash through three Japanese banks and depositing that money into Kajiyama’s account at the Hong Kong bank in February 2003.

Police said Doden was a private banker who handled a wide range of financial services, including asset management and tax advice, for wealthy clients.