From the Super Mario Wiki
The Hero's Journal is an item found in Paper Mario: Color Splash.
It is one of four items Mario must retrieve for Justice Toad in Cherry Lake. It is found north of Justice Toad's hiding place, and left of the entrance of the screen, where there is a Pry Guy who is snooping through its contents. To obtain it, Mario has to defeat the Pry Guy. When Mario gives the journal back to Justice Toad, he acts defensive and describes it as "just something [he] was doodling in," then tells Mario not to worry about it.
As the Pry Guy reads aloud, the journal (or a part thereof) reads:
Names in other languages