Tunic is a reasonably lengthy game for an indie title, but it’s hard to blame you if you feel the need to plumb the world for all its secrets. This can be helped with the inclusion of New Game Plus, which will allow you to carry over all your collected items, except those exclusively used for story progression, such as keys. New Game Plus allows you to effectively sequence break Tunic, as areas limited by item availability are wide-open from the start.
To get New Game Plus, you need to reach one of Tunic’s two endings. The first involves defeating the heir in combat. This is simultaneously the most difficult ending, and the most likely you’ll get first. Essentially, you must restore your corporeal form by visiting all the Hero’s Graves scattered throughout the world. Once you’re back to fighting shape, a rematch (or two, or three) can eventually lead to your victory.
Once success has been claimed, you will be presented the option of either starting over in New Game Plus, or loading the most recent save to search for more pieces of the instruction manual.
If you have already managed to complete the manual, you can simply show it to the heir to get the good ending. This results in one option: resetting to New Game Plus. Don’t despair if you just wanted to search the world for the remaining treasures rather than start over, however. Tunic does create a backup save that you can return to by going into the load menu.