“Regarding the supreme god within the Myriad Gods belief system, Amaterasu, Sasami compiles a report on her PC. Sasami explains how she was trained to inherit Amaterasu’s power, which is handed down through the Tsukuyomi family. Soon after, taking her older brother with her, she ran away. While looking back at her past, Sasami starts to feel a strange sensation from her chest. When she looks, she can’t believe what she sees!” - Official episode guide
This episode is important in filling in the gaps in the anime’s story so far, and learning more backstory on the characters. Key points in this episode are the relationship between Sasami and her older brother, the history of the Tsukuyomi family, and the appearance of the Yagami sisters.
Tsurugi, Kagami, and Tama are named after the Three Sacred Treasures, items that are handed down through the generations to the Emperor of Japan. According to Japanese legend, these three gifts came from Amaterasu and were brought to Earth by Ninigi. In this story, they signify that the power of Amaterasu never left Sasami.
While a grand battle scene takes place in which the shrine is completely destroyed, it is explained that her older brother was never given Amaterasu’s power. Sasami is completely cleared of her affliction that made her be a shut-in and she begins attending school. It seems that we will finally get to see the unmotivated Sasami outside of her house in the next episode.