Shef
Well your discomfort begins to fade as Yuki starts healing you, spirit energy pours forth from her shard, stiffening her hair and illuminating her palms as she focuses healing magic into you. It's, taking a while.
Yuki
Hmm okay so he's not too hurt right now so repairing the damage isn't too tricky, thing is, your healing isn't removing the poison, at least, not quickly.
Faith
Okay so you can see the issue too, well, maybe not see, but thanks to your training you can sense it anyways. Manipulating your own magic, it's made you a little more aware of other people's magic too. The poison affecting Shef? It's a spell, a pretty nasty one too - it's attacking his central nervous system, but it's focusing on his upper spine, trying to effectively decapitate him, trying to sever the connection between brain and body. That is, until Yuki started healing. It seems to actually recoil from the spell, dispersing in its wake before refocusing and dispersing again. It's not targeted you realize, rather it's algorithmic, it's using something to guide its targeting, though you doubt it's designed to combat healing magic - it's dispersing and shit yeah, but it's still getting eroded away and the damage is still being undone. Any delay you see is more from Yuki's magic being geared more for repairing than spellbreaking. You meanwhile, you might be able to speed things up a little, tear the damn thing out yourself.