A recent Health Ministry report showed that a number of Japanese cities were still finding traces of Fukushima related contamination in their drinking water. The amounts found were low but they did include cesium 134, the shorter lived contaminant from Fukushima Daiichi. A strontium 90 test was not conducted on these samples.
These cities had traces found in their drinking water:
Sendai city, Miyagi Prefecture
Fukushima city, Fukushima Prefecture
Maebashi city, Gunma prefecture
Niigata City, Niigata Prefecture