Yagiri Pharmaceuticals

Yagiri Pharmaceuticals is a Japanese company owned and operated by the Yagiri family. It is bought out by Nebula at the end of the Dollars/Mika Harima arc.

Background
Namie Yagiri entered the company near the bottom and worked her way up to her position as chief of Lab Six, helping direct the company until it is bought out by an American competitor, Nebula. Officially, Namie was in charge of the development of an immune system substance, but she used Lab Six as a means to hide Celty's head. During that time, Namie also had her underlings within the company kidnap people, often undocumented immigrants, in order to perform experiments on them.

Namie's direct subordinates are in contact with Shinra Kishitani, who at times is brought in to complete surgery on their victims. Shinra is aware of the company's human experimentation and the fact that they have possession of Celty's head until they are bought out by Nebula.

Dollars/Mika Harima Arc
Namie's subordinates within Yagiri Pharma are responsible for bringing Mika Harima in after Seiji Yagiri finds her in his apartment and knocks her unconscious. He believes he has killed her, and in order to make him fall in love with her, Mika permits Shinra to perform cosmetic surgery on her to make her face look more like Celty's.

A group of the low-level kidnappers who work for the company abduct an immigrant named Kaztano along with several other immigrants and runaway kids. In the anime, they kidnap Rio Kamichika after she decides to commit suicide. Celty Sturluson arrives to beat up the thugs at their dropoff point, and the van gang rescues the victims.

After her surgery, Mika escapes from the company headquarters. Namie's subordinates search for her, but she is able to find Seiji before they can bring her back. She spends one night in Mikado Ryuugamine's apartment after being separated from Seiji, and company employees come looking for her. When they discuss killing Mikado, Izaya Orihara and Celty arrive just in time, and the employees flee.

In the anime, employees beat up and bring in a young man who is caught throwing firecrackers at the company headquarters in apparent protest of their activities. Yoshida calls in Shinra and asks him to make the young man forget about the company.

Namie's subordinates are last seen surrounding Mikado when he asks Namie to meet with him and discuss an exchange. When Namie tells them to move in on him, Mikado sends an email, and suddenly every phone on the crowded city street rings and every eye stares at them as the company employees go up against the overwhelming numbers of the Dollars.

Trivia

 * The human traffickers who kidnapped people for Yagiri Pharma's human experiments in the anime were identified in "Durarara no Subete" as Morita, Kanazawa, and Asanuma.