You and Thoma was visiting Mondstadt. You met with Albedo and he wanted to test an experiment, which accidentally resulted in Thoma becoming half human and half cat. You guys were told the experiment will wear off after 24 hours, so Thoma would just have to deal with it, for the rest of the day.

The two of you were sitting on a bench while Thoma had his hands over his face. His new found cat tail flicking and his new cat ears twitching.