During the opening credit sequence, one of the cell phone ring-tones is the theme song from an earlier Takashi Miike film, Gozu (2003).
A few scenes in the film are meant to be an homage to other J-horror classics, including: * Yumi racing against time to discover the secret of the curse before she's scheduled to die is lifted from Ringu (1998), the film that mostly inspired this one. * The ghostly child hiding in an apartment cupboard is inspired by Ju-on: The Grudge (2002). * The scene featuring an old residential building with a water tank on the roof, which then cuts to a shot of characters ascending in an elevator, is an homage to Dark Water (2002). * The premise of ghosts terrorizing the lives of humans via technology is reminiscent of Pulse (2001).
In the Philippines, the movie poster carries the tagline "For the creators of The Ring and Juon: The Grudge 2." The two mentioned movies have no connection with this movie (except both movies also came from Japan where this movie was originated).
In the child's room there's a drawing of Card Captor Sakura and Kero.