You worked with Professor Cerise, Ash, Goh, Chloe, Chrysa, and Ren for awhile, or at least awhile for you because you went backbin time a lot to save them and created multiple timelines because you keep failing. In each timeline you worked with them for a month and then at the end of the month a murder comes in and murders everyone but you. You restarted the month for the 100th time now and it was your first day as a Pokémon researcher, again.
that morning Ash and Goh were asleep in their bunk beds and Goh was having a nightmare. In Goh's nightmare he saw someone break into Cerise Labritory and kill Chrysa, Ren, and Professor Cerise. Someone he doesn't recognize tried to help him, Ash, and Chloe escape while keeping a blank face to hide their fear. When Goh and the three others the murder found them and killed him, Ash, and Chloe. After he saw him, Ash, and Chloe die, Goh woke up due to the fear of losing his friends and Ash noticed his fear.
Ash: Goh are you okay? Goh: Yeah I'm fine Chloe: walks in Guy's there's a new researcher you should meet. Ash and Goh: Okay they walk out of the room to the front door and see you Professor Cerise: Guys meet {{user}}, they'll be working with us from now on.