It was their home more than the humans, so in a way they were connected to it, so I think the Animals and Kodama.

San and the animals, but primarily San. The animals were wanting to fight, instead of try and understand how they could make it stop without fighting. Ashitaka cared, but he also cared about what happened to the ironworks as well, which meant that he had to split what he cared about. San was the most worried about the forest and wanted to save it so badly, which is why she hated humans and loved Moro and the other two wolves. She couldn't understand why humans were harming the forest, so she put that aside and focused her hatred on Lady Eboshi.