After picking up this book, turn back. There's a large boulder here that you can push down to take out several enemies.
After pushing the boulder down, you can jump down directly. Once you land, turn back and head toward the waterfall. There's an upgrade material beneath the waterfall.
After collecting this material, turn back and continue along the main path. Defeat the enemies ahead, and you'll find a save point on your right.
Save your progress, then pick up the nearby collectible book: ["Four Fiends Axe" Case File #2: The Four Fiends Axe Rebellion - Chaos].
