Mu

Death Note, Volume 12, page 188, has these two rules in regards to "Mu": "All humans will, without exception, eventually die." Also, "After they die, the place they go is MU."

These rules can be applied to both:

A. Humans in general

-and-

B. Humans who have used a Death Note

Humans who have used a Death Note and gone to Mu
Light Yagami Misa Amane Jack Neylon Teru Mikami Kiyomi Takada (she used a piece of Light's notebook to kill Mello) L in the film only (he wrote his own name in Misa's notebook before he burned it at the end of Death Note: The Last Name, thus having only twenty-three days left to live)

Humans who may have used a Death Note and may go to Mu
Near (possibly)
 * At this point in time, it is not known whether or not Near actually wrote name(s) into a Death Note. There was only speculation by Matsuda at the end of the series, therefore it was neither acknowledged or denied in canon.

Soichiro Yagami (he almost used Light's notebook, which Misa delivered, in an attempt to kill Mello after learning his real name with the use of the Shinigami Eyes.


 * However, Soichiro only wrote Mello's first name before getting shot in the back, therefore he never killed with the Death Note.

Raye Penber (he unknowingly used a page of Light's notebook to kill the other 11 FBI members)
 * However, Raye Penber did not use the Death Note to kill maliciously (like the other five DN users), which may or may not have affected his fate after death.

Speculation about Mu
In most instances, Mu is regarded as the Shinigami Realm. However, this is not canon, and until further information from Ohba or Obata is known, it has to be considered as speculation.

The term "Mu," as it is used in Death Note, most likely originated from the name given to an Atlantis-like lost continent written about by James Churchward in 1926's "The Lost Continent of Mu, Motherland of Man."

-Mogturmen 21:40, 22 September 2008 (UTC)