Ultra-class Mystic Code given to Chaldea by the Atlas Institute.

It is a compass that assists navigation in the Space of Imaginary Numbers, and it is also an unbreakable needle that indicates proof of existence in the Space of Imaginary Numbers.

A measuring instrument for moving unwaveringly towards a “predefined destination” in the Space of Imaginary Numbers where “direction, distance, time” change randomly (or rather, they cannot be defined).

Here is the process done during an Imaginary Number Dive:

- First, calculate the distance and output to the destination in normal space.
- Dive into the Space of Imaginary Numbers.

At this point, no gauge can observe the situation outside the vehicle. - Here the Paper Moon’s map is deployed.

Since only the Paper Moon can ascertain the direction, distance, and time in the Space of Imaginary Numbers, the ship must advance along the route indicated by the rapidly fluctuating gauge of the Paper Moon. - When the destination is reached, emerge from the Space of Imaginary Numbers and go out to normal space.

The end of the process.

The time difference between past and future in the Space of Imaginary is corrected using the Shadow Border instead of the Paper Moon.

The origin of the name Paper Moon comes from the concept of “unify coordinates by writing something of a higher dimension on a plane.” The creator says that it has the image of a flat moon pasted on a “universe of aluminum foil” like the ones children make in Arts and Crafts.