My apologies, this is a bug. It will be fixed in the next update. This is not the end of the game; it happens when Tairy levels up before Trelly.
For now, there are two solutions;
- Wait for the next update (Slow way),
- Restart the game by leveling up Trelly to level 2, then Tairy to level 2 (Fast way).
I'm really sorry for the inconvenience! I'm working to send an update as soon as possible!