Smartphone app "Chikan Radar" is joining the fight against gropers on trains, offering users a map showing where attacks took place and sightings of assailants.

As it can sometimes be difficult for passengers heading to school or work to fight back or ask for help if they are assaulted, former Yahoo Japan Corp. employees developed the software to make such information easy to share.

The app, the brainchild of start-up QCCCA Inc., has been available for free since September.

"I hope data on such cases are displayed to show clearly how serious the issue is, prompting further countermeasures," said Nari Woo, CEO of the company.

Users of the service who are victimized or witness a groping incident can open the app and make a report. Six types of offenses can be registered, including "molestation," "stalking" and "camera voyeurism."

The dates and locations are automatically registered based on smartphone data when a user agrees, allowing information on groping attacks to be shown on maps in the app. This also enables a user to see how many groping reports there have been at each station.

If users register their accounts on the Line messaging app, detailed data about the train lines and other factors can be input, making it possible to check the frequency of such attacks and when they occur at each station.

According to QCCCA officials, Shinjuku, Shibuya and Ikebukuro stations are the most frequent stations reported, as they are more crowded than other stops.

Chikan Radar also has a function to drive potential gropers off. The feature becomes activated when a user enters data about a groping or stalking case. The app shows a fake phone call screen and sounds a ringtone. When the user taps "answer," a woman's voice can be heard.

Another feature, added by Jan. 15 and available when location data sharing is permitted, allows users to receive notifications when there is a groping report for the same train car.

Chikan Radar has gained more than 53,000 users since its release, with a total of 2,400 cases registered. Reports cannot be made repeatedly by a user in a short period of time.

There were 2,943 cases of molestation, violating local anti-nuisance ordinances, in 2017, according to a 2018 police white paper. For the same period, there were 269 forced indecency cases in trains.

A survey conducted by the National Police Agency in urban areas in 2010 revealed that 89 percent of women victimized by gropers said they did not report the incident to police.

QCCCA said it has no plan to charge for the use of Chikan Radar.

"If the number of users reaches 1 million, the service will provide valuable big data," said Woo, referring to a plan to sell the collected information to private companies, police, municipalities and other entities so that it can be reflected in security measures.