The Sibling’s Mask is a smaller copy of Taro’s Mask for your Rot Spirits. This adorable fox mask can be found in the Forgotten Forest, but it is hidden. You might walk right past it without even knowing. Keep your eyes peeled to find it and know where to shoot your bow. Here is the mask’s location to make it easier.
Sibling’s Mask location
After reaching the Forgotten Forest, you will be greeted by Rusu. He will talk to you about the shrines. Once you are done talking to him, take the path to the right of the shrine he is standing by. This path will lead across the river and over to a corrupted area.
Clearing out this corruption is a chore. There are a bunch of enemies that spawn here. Some of them are melee focused while others using ranged attacks. Keep your guard up so you don’t get hurt. After clearing out the corruption, Rusu will spawn in (and avoid any combat). To the left of Rusu, you will see a log jutting out from the cliff over the water. Hop down on the log with the symbol on it. A flower will open up on the trees in front of you as in the image below.
You should know what to do from here. Shoot an arrow from your Spirit Bow at the flower to be pulled over to the large stump. The chest will be waiting for you when you land. Open it to get the Sibling’s Mask.