After finishing the fourth chapter of the game, you can opt to save and go to the title screen, from which you'll be able to use this file to start a "New Game+". This will let you bring all sorts of data, including items, money, character builds, asterisks, and more, to a new file.

Furthermore, if, during the new file, you press Start once you gain control of Yew in battle, as if activating Bravely Second, you will be able to continue to the second half of the storyline. Take note that this will disable New Game+ for this file again until you beat the game. You will also be able to redo all of the asterisk sidequests in this file all at once, letting you pursue the asterisks you missed the "first" time around.

After beating this "true" ending to the game, you will unlock a more proper New Game+ option again, this one letting you restart from any chapter of your choice. (Note that chests will not respawn unless you start from the prologue.)