"Even a Chance Acquaintance is Decreed by Destiny" is the first episode of Durarara!!x2 Ketsu and the fifty-third episode overall of the Durarara!! anime.
Celty and the others who have gathered at her apartment form an alliance.
adapted from what manga or LN chapter?
To the meeting that happened in Celty's apartment.
In order of appearance (not including OP)