Oh no, I know exactly how this will end and it's going to be horrible.
At the end, Chishiro's gonna get bullied again and but Kisaki will be nowhere to be seen. Her shoes will get thrown into a tree and she'll flash back again to when she was younger and Kisaki helped her. Only now Kisaki IS THE TREE and the branches creak and manage to give the shoes back to Chishiro before she freezes up permanently. If the author wants to stab us extra hard, she'll freeze up with her branches curved to shape a heart, and then maybe the spot becomes famous for new yuri lovers to visit in hopes of making their relationships blossom, with an Old Lady Chishiro telling the legend of the heart-shaped tree to a some younger girls.