[Though Chrom can't see what Jaune's shadow is doing ability-wise, he nonetheless moves fast to interpose himself between both of them, sword drawn, but held defensively rather than pointed in challenge.]

Jaune, take a breath. It's starting to attack because you're not accepting that this is a part of yourself. It will continue to lash out until you do. Do you understand?

[His head turns in Jaune's direction, but his gaze stays fixed on the shadow.]

If you keep rejecting it, it will possess you, and we'll be forced to fight you ourselves. I'd rather avoid that possibility, wouldn't you?