There's a lot of confusion surrounding Wuthering Waves and how it handles its missions, like Shadows of the Past, which asks you to wait for a message that never seems to appear.
How to Wait for Xiaoyu's Message in Wuthering Waves | Shadows of the Past
After you complete the first part of the mission, a message will appear asking you to "wait for Xiayou's message". It's a short piece of text that sounds simple enough, but it causes a lot of confusion among many players because it doesn't tell you how long you have to wait or how to get the message in the first place.
Several hours have passed, no message comes and now you are here looking for answers on what to do. So let's not waste another moment of your time.
To wait for Xiayou's message in Wuthering Waves, you will need to wait more than 24 hours from the time you completed the first part of the quest line.