Durarara!! - 1x17 - 有為転変- Followmy.tv

Sonohara pokes Niekawa with Saika, and shows her a flashback of how she became its wielder. Sonohara's father was an antiquities dealer, and constantly beat up her and her family. Her mother then got possessed by Saika, killed her father, and committed suicide. Sonohara then grabs the cursed blade, and becomes its wielder. Meanwhile, Shizuo beats up Niekawa's "Saika children," flashing back to his past. Sonohara then assimilates Niekawa's Saika, and as a result takes control of all of the Saikas in Ikebukuro. Sonohara apologizes to Celty for attacking her back in Episode 5. Mikado later visits Sonohara at the hospital, and after realizing she has met the "unusual people," warns her to stay away from the non-normal. As a result of Niekawa's assimilation, Sonohara has gained her and all of the Saika's memories; she suspects that Izaya is up to something. Mikado is later shown contacting members of the Dollars, but it is unknown for what reason. The episode concludes, as Izaya's plot deepens further; he is revealed to be behind several events in the slasher arc. He has caused a split of the city's population into different "factions;" Saika/Sonohara's army, the Yellow Scarves, and the Dollars; and knows that they will fight amongst each other. Kida, not knowing Anri Sonohara's true nature, retakes his place as the leader of the Yellow Scarves. He suspects the Dollars to be responsible for Sonohara's injuries, and vows revenge.