(hei feels the knife pull through skin and regrets it — only momentarily. both of them had the choice to standby, hang back, keep their noses out of his business. they didn't. now they're bleeding, the mermaid struggling to hang onto her forearm while simultaneously shouting for help in a foreign language, and sheryl—

well, he turns on sheryl with a sheathing of his blade.

it's as much justification as he needs.)

This is what you deserve, if your first instincts are to grab a dagger. (or the hand holding one.) You didn't need to intervene, that fish got her warnings and ignored them.