So basically it's about (SPOILERS)
A teenage non-cis individual who formerly identified as female who took a Gender Studies course in her first semester. She learned from he lesbian professor that there are an infinite number of genders and began to self-identify as a tree.
The tree's pronouns are tree, tris, trirs, and treeself. Please be sure to identify tree as such or you are an evil, bigoted treephobe.