Apartment 1303 is a Japanese horror film, directed by Ataru Oikawa, that revolves around a woman who investigates a series of suicides in her late sister's apartment. Based on Ju-on horror author Kei Oishi's original novel.
Living on her own for the first time, Sayaka celebrates with her friends at her new 13th-floor apartment. During the party, she is seen acting strange before jumping to her death from her balcony. A little girl picks up a teddy bear lying near Sayaka's body and says: "There goes another one."
At Sayaka's funeral, her older sister Mariko sees the ghost of Sayaka, who whispers: "Mom pushed me." Their mother, deeply devastated by Sayaka’s death, seems to be falling into a world of insanity, which worries Mariko. At Sayaka's apartment, a little girl appears from next door and informs Mariko that all women who lived in #1303 have died.
While Mariko clears out the apartment, she repeatedly catches sight of Sayaka. She then comes across an earring that looked as if it’d been ripped out of someone's earlobe. Mariko wonders if this might be a clue. She meets a police detective, Sakurai, who reveals that he’s been investigating a series of suicides at #1303 and he doesn’t believe it’s a coincidence. Mariko gives him the blood-streaked earring, believing it belongs to a previous tenant.
Mariko soon comes across a book about the first two tenants who lived in #1303: Yukiyo Sugiuchi and her mother. The mother became abusive towards Yukiyo for hiding food and having her ears pierced, which prompts her to rip the earring out of Yukiyo's earlobe. Yukiyo reacts defensively to her mother’s violence with a butcher knife, then watches while her mother crawls into a closet, where she bleeds to death. Six months later, the landlord reveals his plans to have Yukiyo and mother thrown out for failing to pay rent.
Upset and afraid, Yukiyo sees the ghost of her mother, who has been tormenting Yukiyo since her death. Yukiyo picks up a teddy bear, walks to her balcony and jumps to her death. Mariko discovers that since Yukiyo’s death, the next four tenants – with Sayaka as the latest – had moved into #1303 and eventually jumped to their death. The police ruled each case as a suicide.
Mariko learns her mother plans to visit #1303 to see Sayaka one more time and rushes to save her. Unknown to Mariko, the apartment has been rented out to several college students, who throw a party that night. During the party, Yukiyo pushes girls over the balcony. Mariko arrives and rushes to #1303. Yukiyo appears and Mariko accuses her of killing the previous tenants but Yukiyo denies this, revealing that her mother is the one who told her to throw them over because they were evil. Mariko returns Yukiyo’s earring to her while promising to look after #1303. The spirit seems to accept this and vanishes.
As Mariko awakens the following morning, Yukiyo pushes Mariko against the balcony and tells her that her mother has only one daughter. Mariko notices Sayaka watching just as she falls to her death. Standing next to her mother, the little girl says: "There goes another one." Then she and her mother vanish.