The third film in the hexagon project J-horror Theatre. The two first films are Infection (2004) and Yogen (2004).
Takako Fuji portrays the hotel maid. She had previously collaborated with Takashi Shimizu on the Ju-on: The Grudge (2002) series and the American remakes known as The Grudge (2004).
(at around 42 mins) During the first scene in the hotel when Nagisa attempts to hide from Professor Omori, she first attempts to enter a locked room 237. This may be a reference to The Shining (1980).
"Reincarnation" was the Brazilian Portuguese title chosen for Birth (2004), released the year before. Thus, this film was titled "Reincarnated Souls" in Brazil.