Uhm, judging from the artist's other picture that was uploaded, either that's just some unfortunately placed shadowing on Yuri's face or he is about to go nuts on Rita.

Considering those two, it could go either way. . .

I think it is just bad lightning and the shadowing makes it look like something bad is going to happen guys. Basically just see the candles in the foreground. Well in Yuri's hands the sword and how it is angled the blade would cause a shadow that would darken around the area of the eyes.

Yet maybe I am just trying to put a logical answer to two characters that are slightly illogical with each other. It is rather cute.

From the thumbnail, I thought it was a Whip, I am dissapoint....