Note: This game is also titled Mana-Khemia: Gakuen No Renkinjutsu Shitachi.
Successfully complete the game and save when prompted. Then, reload any save before the final Boss, and go to the world map to access a location called "Old School Building". A section inside there is called the "Forbidden Zone". There is a teleporter deep in the dungeon that can be used to access a bonus dungeon. The bonus dungeon has powerful monsters, an alternate stronger final Boss, and an appearance of the Boss from Atelier Iris 3. Additionally, your cleared saved game file will unlock the "Extras" option at the main menu. The "Extras" menu has "Gallery", "Database", "Music", "Cast", and "Endings" options. Note: Each subsequent time the game is completed, more endings will appear in the "Gallery" and additional entries will appear in the "Database".