KAMPONG LAMBE, Indonesia — A Tokyo surgeon this week set off from Indonesia on a 100-day voyage to trace one of the paths believed taken by ancestors of the Japanese some 3,000 to 10,000 years ago.

Departing from Kampong Lambe, a small fishing hamlet on Sulawesi Island, on Monday, Yoshiharu Sekino is leading a 10-man team in two handmade sailboats from Southeast Asia along the Black Current. He plans to arrive in Naha, Okinawa, around July 20.

Four Japanese, including Sekino and two of his students, and six Mandar fishermen from a local tribe are taking part in the trip — five people for each boat.