Final Curtain Arc

ARC undefined The Final Curtain Arc is the ninth and final arc of the Durarara!! series, as well as its longest one. It can be further divided into three sub-arcs:

Kadota's Coma Arc
After Kyouhei Kadota is injured in a hit-and-run by an unknown assailant and falls into a coma, the other members of the Van Gang furiously try to find the culprit and take revenge. Meanwhile, Izaya Orihara and his newly formed alliance fight against the Jinnai Yodogiri group, ultimately dismantling the organization and setting its true leader, Kasane Kujiragi, free.

Haruna Returns Arc
Izaya Orihara is kidnapped by Slon, controlled by Kujiragi's Saika, and then eventually rescued by Mikage Sharaku and Kine. When going to the hospital, Izaya runs into Anri Sonohara, and instills anxiety in her, before being driven off by Erika Karisawa. Manami Mamiya steals Celty Sturluson's head from Izaya and throws it in public, causing an uproar. Anri, now in inner turmoil over her perceived lack of humanity, is approached by Haruna Niekawa, who freed herself from the control of Anri's Saika, and the two do battle before being interrupted by a third Saika user, Kasane Kujiragi, who coincidentally happened to be in the area. Kujiragi offers to buy Anri's Saika from her, but after some deliberation, Anri refuses the offer. Meanwhile, Shinra Kishitani and Celty form a temporary alliance with various other individuals who ended up at their apartment, including Namie Yagiri, Seiji Yagiri, Mika Harima, Walker Yumasaki and Saburo Togusa, calling it the Guild.

Valkyrie's Descent Arc
Izaya resolves to exterminate Shizuo once and for all. Celty's head, now in police custody, is stolen by Vorona, who undertook the job from Kujiragi. While escaping, Vorona runs into Shizuo Heiwajima, newly released from prison, who assumes Vorona's involvement to be due to Izaya. Shinra is kidnapped from his home by Kasane Kujiragi, which sends Celty into a frenzy, transforming into a giant ball of darkness and pursuing Kujiragi. Chikage Rokujou picks a fight with Masaomi Kida, but then saves him when Ran Izumii and his thugs intercept them. Russia Sushi is targeted by Takashi Nasujima's army of Saika-infected humans, seeking to infect Tom Tanaka in order to use him as a trump card against Shizuo. Aoba Kuronuma and the Blue Squares also get involved on Mikado Ryuugamine's orders. After leading Celty to a convenient location, Kasane Kujiragi attempts to sell the Dullahan to Seitarou Yagiri, but after being intercepted by both Shizuo and Shingen Kishitani along with Egor, the deal goes under, and Celty's head is reunited with her body by Shingen, recovering her memories as a Dullahan and Valkyrie. Meanwhile, Izaya and Shizuo have their final battle, Izaya using every trick in the book to try and kill Shizuo, but nothing claims the man's life. Vorona tries to get involved, but is stopped by Mikage. Masaomi and Chikage approach the area, trying to find Mikado. After Chikage leaves, Masaomi comes face to face with his old friend, Mikado, who was hiding from him. Mikado explains his plan to end the Dollars, turning them into an urban legend, by using the Dollars name to target both the police and the Awakusu-kai, using the gun received from Ran Izumii in the process. Masaomi tries to stop him, but Mikado shoots him in the leg, and then attempts to shoot himself in the head, explaining to Masaomi that he knows he will end up hurting the ones he cares for if he remains alive. Meanwhile, Izaya, having sustained many injuries from Shizuo, nonetheless keeps fighting him, drawing him to the most populated area, in an attempt to get Shizuo to kill him in order to have him branded as a true monster in the eyes of society. Shizuo hits him head on with an electric pole, but before he can finish Izaya off, Vorona stabs Izaya, trying to kill him herself so that Shizuo doesn't have to bear the responsibility. At the same time, Kine, Tom and the staff of Russia Sushi break out and begin to fight with Nasujima's Saika zombies, and in the confusion, Kine rescues the injured Izaya. Then, Celty stops the fighting and prevents Mikado from killing himself, in order to make amends for disturbing the city. While trying to escape, she is stopped by Shinra Kishitani, who, with the help of Shizuo, severs Celty's head again using the Saika bought from Kujiragi, keeping her from leaving. Mikado, having reunited with Masaomi and Anri, help carry Masaomi to the hospital before Mikado is stabbed by Nasujima while protecting Anri from him. Mikado falls into a temporary coma before regaining consciousness some time later. Celty's head is sent to Nebula for safekeeping. Izaya leaves the city, just barely surviving from his injuries.