NHK reported that according to police, the girl was walking in the Nakano ward of Tokyo on June 18 at 8:00 p.m. when the suspect approached the girl from behind and touched her inappropriately. Afterward, the suspect fled the scene. The girl went to police, who analyzed security camera footage to investigate. Police discovered through security footage that about an hour later, a similar incident on a nearby road with a different female middle school student occurred, involving a suspect who resembled Matsuki.
According to police, Matsuki told police "there's generally nothing incorrect" with their accusations.
Viz Media published the first three chapters in English simultaneously with the Japanese release, and then began regularly publishing the manga digitally in December 2018. Shueisha's MANGA Plus website also publishes the manga in English digitally.
Update: Updated article with more details of incident, as reported by NHK. Source: NHK