The old anonymous group chat, populated by some of Ikebukuro's most peculiar residents, receives a sudden addition: Saika, a cryptic user who occasionally appears to send messages that make little sense. While everyone dismisses these as spam, a curious connection soon emerges between Saika's messages and a recent string of slashing assaults. Dubbed the "Slasher" by the media, the attacker's rampage continues. Meanwhile, Anri Sonohara is advised to stay away from a teacher with a history of dating minors. Although she now has friends, Anri still suffers from bullying; during one incident, she comes face-to-face with the Slasher, becoming the first person to survive the encounter unscathed. Elsewhere, a reporter covering a story about the so-called strongest man in Ikebukuro is viciously attacked by the Slasher. As the top contender for the title of strongest man, Shizuo Heiwajima sets out to hunt down the mysterious aggressor. In his latest discovery, the infamous information broker Izaya Orihara reveals that the Slasher might just be Ikebukuro's next supernatural threat.