Towards the north eastern side of the map there is a cave with two seperate paths at the entrance. This doesn't matter whether you go down the safer path to the left or fall down the waterfall to the right.
At the end is a chamber with tons of candles all over the cavern. In the middle on the right wall, is an shrine to a girl who died here. On the shrine is the note.
Warning. Go left and follow the path out up the slope to get out. Pretty much all other paths lead to death at this point. Once you left the cave, feel free to explore by turning right after dropping down from the ledge.