>>43751995KSP2 just came out, so I admit I'll be a little busy, but I'll try to at least get you a rough outline rentry tonight. For now, these are some of the details I wrote out to another anon last time:
Essentially the story would start out with him having some reason to delve deeper into an /uuu/ forest than other sanalites have before. By that point sanalites would know that there are not just cultural stigmas against strangers going deep into the forests, but their tech and their biological cataloging would have shown that the flora and fauna changes somewhat drastically as the forests get bigger and thicker. These changes would not be what zoologists would say are necessarily "evolutionarily driven".
His reason for deciding to go deeper might be up to you. In your first bit of the story he's tracking an animal, but it's dead. Though you do hint at him trying to help the cub though, so maybe he goes deeper into the woods, hoping to find some food for it? The point is, he has to have some reason to not just go deeper into the forest, but *continue* to go deeper, even after things start getting weird.
Since you gave him to me to die anyway, I would start with the assumption that he's already well into the "first" layer of the forest, close to the second. Now that he's decided to spend the night there, he would wake up with some moss in his hair, maybe some under his fingernails as well. Small patches of his skin would seem dry, maybe a little rough, but nothing he wouldn't just chalk up to maybe a dry climate.
As we skip forward in the story, things get worse and worse, to the point where he can't ignore them. The dry patches of skin are turning into bark. The moss in his hair isn't just moss, its vines and leaves and they're growing out of his scalp.
One night he would wake up and see that small roots have grown out of his fingers and toes, some even finding their way into the soil of the forest (if he has a tent, they poked through it). In desperation he might try to yank the new growth off of his body, but the larger ones refuse to come out, the tugging causing extreme pain, and the small ones he can manage to rip out cause bleeding wounds. The blood that seeps out of these wounds is still red, but with just a slight tinge of green.
Eventually movement would become difficult. The patches of bark on his skin are getting harder, and where they are growing over joints, those become very hard to flex.
