Who are the twins in Episode 1 of Durarara!!x2 Shou? At first, I didn't notice this part because I was too focused on Celty and Shinra's "lovey-dovey upgrade", until my friend told me about this part... 

They are making something weird, or should we call it a weapon - right there on the table?

What I want to ask is, are they assassins? Or do they have another identity besides being obsessed with Yuhei-sama ?
They're Orihara Izaya's little sisters,
 Mairu and 
Kukuri

They appeared in the special in the first season.