Probably drug money.
Probably the Japanese Mafia.

"Created in 1915, the Yamaguchi-gumi is the biggest yakuza family with more than 39,000 members divided into 750 clans (thus making up 45% of all yakuza in Japan.) Despite more than one decade of police repression, the Yamaguchi-gumi has continued to grow. From its headquarters in Kobe, it directs criminal activities throughout Japan. It is also involved in operations in Asia and the United States. Shinobu Tsukasa, also known as Kenichi Shinoda, is the Yamaguchi-gumi's current oyabun. He follows an expansionist policy, and has increased operations in Tokyo (which has not traditionally been the territory of the Yamaguchi-gumi.)"
http://en.wikipedia.org/wiki/Yakuza

A DNA test could provide answers.