The police official, who spoke on condition of anonymity as is often policy at Japanese bureaucracies, said the case was related to the reports about a stalker and pupil images. Police described Sato as an "avid fan."
Public broadcaster NHK and other Japanese media reported this week that details in the woman's selfies were used to identify the train station she frequented. They said Sato looked at other images she shared, such as her apartment, to figure out where she lived.
Police say he hurt her and committed indecent acts, such as groping her after accosting her from behind and knocking her down. Japan has many young female performance groups. Tokyo Shimbun, a metropolitan daily, which reported on the stalking case, warned readers even casual selfies may show surrounding buildings that will allow people to identify the location of the photos.
It also said people shouldn't make the V-sign with their hand, which Japanese often do in photos, because fingerprints could be stolen. Cyberstalking has been a problem for years, with criminals and perpetrators of domestic violence using hacking, clandestine activation of microphones and cameras and other methods to track their victims.
It's unclear how prevalent the use of high-resolution photos to locate potential victims might be.