Attempt to leave Kamiki three times immediately as Amaterasu returned to the village, as there is nothing to do here, other than talking with the villagers. The third time she attempted to leave, agree with Issun that she wants to leave. If Amaterasu desires to stay, she will find villagers around the village, celebrating. Susano and Kushi can be found in front of the statue of Nagi in the River of the Heavens. After listening to all participants of the festival, Issun will eventually suggest finding the four remaining Celestial Brush techniques.
When the festival is done with, leave the village and head to Taka Pass. At the far western end of Taka Pass is the City Checkpoint, the next destination.