Kokona Aoba
Aoi and Hinata meet Kokona at the slopes of Mt. Takao, where she headed in the hopes of seeing dwarf flying squirrels, but was foiled when one of her shoes’ soles partially tore off. Aoi performs some emergency repairs, though, and the three head back down.
The three of them, plus Kaede, eventually forms a circle of friendship through their common interest.