After releasing Kaguya from her cell by manipulating the Emperor during his coma, she will run out to the front of the palace, and when Amaterasu and Issun approaches her, she will speak about her fragmented memories and these coming back to her in pieces. After piecing these fragments together, Kaguya will have a sudden realization of where her memories are held, with the Royal Crest, and run off. Follow her there.
At Sasa Sanctuary, in the bamboo grove amid the bamboo forest at the back of the inn, Kaguya will have a brief reunion with Mr. Bamboo. But then, she expresses doubts regarding her origins and the Royal Crest on the ground in the grove. Then, suddenly, a circle of light appeared on the ground, exploding into a hole. Kaguya then jumps down into the hole, exclaiming that she has to uncover her origins. Amaterasu will jump after her, and a digging session will be started. After reaching the bottom, Kaguya will mark a specific block of stone, and when dug up, will reveal a giant state-of-the-art steel rocket built in the shape of a bamboo shoot. It is now that Mr. Bamboo reveals that Kaguya was actually their adoptive granddaughter, and he retold the day when the bamboo rocket crashed down to Sasa Sanctuary, and him and his wife adopting Kaguya. After a conversation, Kaguya will bid her farewell to her adoptive grandfather, and gives Amaterasu the Fire Tablet as a token of her appreciation. She then enters the rocket and departs for her origins. Now, leave Sasa Sanctuary and return to Sei'an City.