"Mouth of Honey, a Needle in the Heart" is the eighth episode of Durarara!!x2 Ten and the forty-eighth episode overall of the Durarara!! anime.
Heaven's Slave is both the name of a secret organization and the highly addictive drug they are pushing onto the market. The group, led by a mysterious man called Kumoi and his subordinate Hiroto Shijima, is an outfit of Raira College students who model themselves after the Dollars, communicating with their drug pushers solely online and via burner phones. They are seeking to join forces with Amphisbaena next, a small, secretive group that has been running an underground casino and operates an advanced bugging system that they use on their clients.
The Awakusu-kai hire Izaya Orihara to look into Amphisbaena, who are operating their casinos on the yakuza organization's turf. The group abducts the information broker during his investigation, and their leader, Earthworm, enjoys her playful torture while she questions him. When finally her subordinates are supposed to arrive with his twin sisters, Mairu and Kururi, Shijima and his Heaven's Slave thugs arrive instead. While Shijima proposes joining forces, Izaya's assembled group of allies manages to take the upper hand.