Takahiro Shiraishi confessed to the police that he had looked on Twitter for people considering killing themselves, and had lured them to his apartment, local news outlets reported.
TOKYO — Over the summer, the man told his father that his life had no meaning. Then he went looking for others who felt the same way, and apparently killed them.
The man, Takahiro Shiraishi, was arrested on Tuesday, a day after the police visited his apartment almost 30 miles southwest of Tokyo and found the dismembered parts of nine bodies. Japan was riveted as the news media disclosed more grisly details from the second day of the investigation, reporting that Mr. Shiraishi, 27, had confessed to finding the victims, who he said were considering suicide, on Twitter.
In Japan, a low-crime country, it is the grimmest such case since a former employee of a center for the disabled went on a knife rampage there, killing 19 people last year.
Mr. Shiraishi’s case, involving social media suicide pacts, connections to Tokyo’s notorious red-light district and neighbors who did not report a noxious smell coming from the suspect’s apartment for months, has the hallmarks of a grotesque thriller novel or horror movie.
Japan has the third-highest suicide rate of the world’s richest countries, after South Korea and Hungary, and its government has prioritized suicide prevention, monitoring suicide-related message boards on the internet, among other measures. The Japanese murder rate, by contrast, is one of the lowest in the world, making the news media all the more obsessed with the ghastly details of the current case.
Television reporters spent a good part of Tuesday and Wednesday training their cameras on the building in the city of Zama where Mr. Shiraishi lived, or showing footage of the suspect covering his eyes with his hands as the police drove him to meet with prosecutors Wednesday morning.
With the police officially saying very little, it was left to the Japanese news media to report details leaked to members-only “press clubs” for crime reporters.
Although the police have so far charged Mr. Shiraishi only with “abandoning bodies,” news reports on Tuesday described him as a serial killer who sought people who were thinking of killing themselves and who had expressed their dark thoughts on Twitter.
