Firtrich, like many other Animon in LumenTale: Memories of Trey, has a unique evolution method. It doesn’t evolve by simply leveling up. Instead, you’ll need to take it to a specific location in the game.
Firtrich evolves into Pinouflage, a much more elegant version of itself. If you’ve scanned the Grass type enough times and unlocked a higher research tier, the LMD will tell you that the creature evolves by “Level +,” meaning you have to get it to a specific level and meet an additional criteria before it will change into Pinouflage. The game won’t tell you exactly what that is, but you won’t be completely left in the dark.
As is the case with Kinedge’s evolution, LumenTale gives you an additional hint on how to evolve this tree ostrich. If you go to the city of Altipetra, an eastern city by the volcano in Mythos, you’ll find a drawing in one of the houses, as shown in the image below. It’s a fairly dark image, but it’s light enough that you can make out a drawing of Firtrich along with “Area 11” on it. The image suggests that combining the two nets you something new.

As we know from the LMD, taking Firtrich to Area 11 won’t be enough to get it to evolve into Pinouflage. Unfortunately, this image doesn’t tell you the level you need your Firtrich to be before it’ll evolve, but in my experience, your Firtrich has to be at least level 37. If your Animon isn’t that level yet, you’ll need to battle wild Animon or Lumen in the area, or craft food recipes—like Lampredino, Canerdeli, or Cotolino—at the nearby fountain and then feed it to your Firtrich to level it up.
If you’re not already at Area 11, head there once your Firtrich has reached level 37. There’s no specific spot on the route where the Grass-type Animon will evolve; all you need to do is get to the area, open your party menu, and click on Firtrich. A small yellow arrow will appear next to Firtrich’s icon, and the option to evolve it will be available to you once you click on it.

To make the most out of your journey around Talea, check out our guide on all of LumenTale’s attributes, as well as information on the game’s various Animon types.