In the sprawling world of Genshin Impact, the Traveler’s search for their lost sibling takes them to the Japanese-inspired nation of Inazuma. There, they encounter an Archon named Raiden Shogun who strives to keep her nation isolated from the rest of the world. After resolving the conflict, Inazuma and its people are free to visit other nations once more.
Inazuma introduced many new popular playable characters to the game, but Ayato has been a long time coming.
Source: https://www.distractify.com/p/when-does-ayato-come-out-in-genshin-impact