I don't know how to tell much about it, without spoiling too much, so maybe this text contains some spoilers for the game.
You are taking of the control of a boy who is "friends" with a big monster. That monster is getting aggressive when eating frogs, which appear sometimes within the levels.
You have to solve (fairly easy) puzzles along the way.
The whole thing is placed in a sort of favela-themed world.
It looks beautiful and the game is very touching, due to the very mature and imho unique story.
Don't expect mindblowing gameplay or hard puzzles, but the beautifully created world, the characters and the story is what make this game a small gem for me.