According to MHLH (Ministry of Health, Labour and Welfare), Cs-134/137 has been detected from tap-water of Tokyo since October of 2014. The data is from October 2014 to March 2015. The newer result hasn’t been announced yet.
The sample was collected from the tap of Tokyo Metropolitan Institute of Public Health in Shinjuku.
The density was from 0.00178 to 0.003 Bq/Kg. Cs-134 was detected to prove it is from Fukushima plant.
The analysis was implemented by NRA (Nuclear Regulation Authority).
All the other analyses were carried out by Tokyo Metropolitan Government Bureau of Waterworks or municipal governments and the lowest detectable amount was over 0.5 Bq/kg to show none of the actual readings.
Source: Fukushima Daiichi