He's a big boi in this form, so he paces on all fours up to Baku, fangs bared, growling.
He stops suddenly, trying to hold himself back. He's shaking a little from the effort.
The blackness starts to swirl around his legs. He's shaking, trying to hold still and bring himself back to normal so bad...
"Grrrrrr..."
It creeps higher, reaching to his waist. He starts to squirm and snaps a little, then growls at himself
"Grr...nnnn-"
"Nn...hnn..."
It creeps up his torso and neck, he's shaking so badly, trying so hard to resist the urge to snap and attack Baku