The Ikebukuro Calamity (池袋之殃) is the fourth chapter of the second Durarara!! light novel.
Kyouhei Kadota reads the report on the latest victim in the series of slashings, making the victim count raise up to fifty. Kyouhei tries to ask Erika and Walker if they heard anything from the other victims, but the two are immersed in their own trivial topics. They are interrupted when they receive a message on the Dollars forum, informing them that a Dollars member has been attacked by the Slasher.
Elsewhere, Celty discusses with Shinra about the recent attacks when Shinra mentions a similar incident five years prior and the culprit being a wielder of a demon blade known as Saika. Celty initially brushes off Shinra's explanation and decides to go see Shizuo, recalling that the Saika user in the chatroom has repeatedly mentioned his name.
When she meets up with Shizuo, she tells him about the recent slashing with Shuuji Niekawa who had interviewed Shizuo the day before. Celty clarifies she does not suspect Shizuo to be the Slasher, believing that he would not conduct random attacks and that the casualties would have differed. Shizuo initially declines Celty's request to help find the Slasher until Celty admits she has been attacked a few days earlier. Shizuo immediately wants to find the Slasher upon hearing that, but Celty manages to persuade him to wait until she gathers more information. She leaves Shizuo and heads to Shinjuku to meet with Izaya, who tells her more about Saika.
Celty rushes home to Shinra and recites what Izaya told her. Afterwards, Shinra shows her the chat log, where the user Saika had logged on and announced they would be cut more people the following night and the desire to find Shizuo.
- Walker mentions being visited by a 'dream demon' who was a maid. This is in reference to his encounter with a succubus in the Duramp!! gaiden special.
Shizuo: "I just want to be strong. If I'm the cause of all this, then I hate myself most of all. I don't care about fighting. I just want the strength to control myself."