The story is about Ukiyo Hikari, a young girl with amnesia found by Tsumuri on a rainy day. Hikari always had a strange dream about two interdimensional travelers Aether and Lumine fighting an unknown God. One day, Hikari is accidentally pulled into an attack by strange monsters known as Hilichurl. In a dangerous situation, a mysterious voice appeared and empowered Hikari with some kind of power, allowing her to become Kamen Rider Geats: Geats IX Form. Later, Hikari remembered everything, and decided to complete everything that she was unable to complete in the past before losing her memories. Hikari went to Teyvat, where she met Lumine, one of the two travelers she saw in her dream, and Lumine's companion, Paimon. After learning that Lumine is searching for her missing brother, Hikari decides to join Lumine on a journey through the seven nations. On that journey, all three of them gradually discovered the mysteries hidden on the Teyvat continent. Lumine and Hikari have gradually gained information about her brother. And on that journey, they met new friends and together changed the world. Will Hikari finish everything she unable to complete before? Will Lumine see her brother again? And what mysteries are hidden on the Teyvat continent? Please follow the story.