The Devouring Frog in Mortal Shell 2 is a very useful special NPC. In the first few encounters, giving it mushrooms will reward you with treasures worth 2,000 coins. After several exchanges, you'll notice it's on the verge of death. To save it, you need to go behind Mushroom Village and find the woman there. This is essentially the Devouring Frog's romance storyline.
How to Save the Devouring Frog in Mortal Shell 2