(Note: This page features spoilers of the original DN series. Tread lightly. Also, this story's development is in progress. Changes will likely be made to various aspects.)
- All humans, without exception, will eventually die. However, not all will cease to exist in any form (i.e. go to Mu). The spirits of humans that have been affected by a Note (by using a Note regularly or being in possession of one) will remain in existence inside Purgatory, a realm within the Shinigami World. These beings are referred to as the Note-Touched.
- A human being is capable of entering the Shinigami world if a Shinigami invited them. However, if they enter the world while in spirit form, their soul will dissipate and return to Mu.
- Despite the fact that living humans may enter the Shinigami World, that does not mean that they're immune to death. Their scent will attract Shinigami, and if a Shinigami consumes them, they will return to Mu, even if they were affected by a Note but had not yet died for the first time.
- A Shinigami can convert a spirit to physical form. This is the only manner through which a spirit that is contained in Purgatory may travel through the Shinigami World or enter the human world once more, effectively being reborn.
- Aside from the aforementioned experiences (being consumed by a Shingami or entering the Shinigami World in spirit form), there is one more manner that would return a Note-Touched spirit to Mu. Any Note-Touched spirit that is converted to physical form and reborn by entering the human world will return to Mu once said human has reached the end of their second lifespan.
- All of the actions of a Shinigami that are described above (consuming a human in either form, restoring a spirit to physical form, and inviting a human to enter the Shinigami World) are Extreme Level offenses.
- Purgatory is habitable for both spirits and humans in physical form, but a human in physical form must depart from Purgatory and reenter the human world within 12 human hours, or they will automatically convert to spirt form.