The three girls who make up the Ganguros are Haruko, Youko, and Akie.
The Ganguros are a trio of female high schoolers who seem to blame Anri Sonohara for their troubles and bully her on several occasions. They are sometimes seen with their boyfriends, including Hiroshi and Takeshi. They later become victims of the Slasher and are shown leading Haruna's Saika Army in their battle with Shizuo Heiwajima. Their names were revealed in "Durarara no Subete."
The Ganguros appear differently in the manga and anime. In the manga they are light-skinned and are from Japan, while in the anime they are dark-skinned and are foreigners.