It's quite possible that they are in trouble here. Ichimatsu certainly isn't the biggest human they've seen; more than likely, they're far more capable of continuing to struggle even after he's exhausted himself. And unlike him, they are not an adult. They cannot assist him past potentially dragging themself across the ground, using themself as a counterweight at the next tree 'above' them as he drags himself after them.

They have a brief moment, in which to consider this. And then a very familiar sensation seeps into them.

Again, they stay quiet. But their SOUL leaps from their chest in response, a vivid red that shifts to deep blue, almost too quickly for the eye to see. There's no shout. There's no jerk of surprise. They don't look wildly about for the source of what's happening to them.

Chara continues looking straight at sans. And there is no fear, not at the situation, nor at his action, to be seen.