Complete the story, save your game when prompted, and select Continue on the title screen to begin a new game with all the health and ink pots earned in the previous save, as well as bonus items you might have earned.
End Game Unlockables:
|Dark Sun (Dark Chibi)||Beat the game|
|First Sunrise (Chibi Shiranui)||Complete everything|
|Karmic Returner (Original Amaterasu)||Beat the game|
|Moon's Legacy (Made of Ice)||Complete the Treasure Tome|
|Painter's Legend (Ishaku's armor)||Complete the Bestiary|