The Yomiuri Shinbun has run an article on its English site that states burglaries have dropped 30% in Tokyo after the arrest of two groups of Chinese thieves:

The arrest of 16 Chinese people operating in two groups on suspicion of burglaries has caused a 30 percent reduction in the number of burglaries and thefts in the Tokyo metropolitan area, it has been learned.

The 16 arrested are believed to have committed about 380 burglaries in Tokyo since autumn in 2005, while the Metropolitan Police Department also found that a member of the group had formed a new group that committed about 300 thefts.

Both groups allegedly would switch off the circuit breaker of the houses they broke into to delay the discovery of the crime by ensuring the resident could not switch on a light and see that the house had been entered.

[...]

According to Suginami, Ogikubo, Nogata and Kitazawa police stations covering incidents in Suginami, Nakano and Setagaya wards, where both groups had been active, the number of thefts and burglaries in the first half of 2007 decreased by 50 percent to 80 percent from the same period in the previous year after the arrests.

The Yomiuri Shinbun’s Japanese language version of this article has the nationality of the criminals in its headline [It reads something like "Crafty Chinese theft group made a killing, burglaries drop 30% after their arrest"], and states that some of them were in Japan as students.