The character, Masami Kurahashi, returns from Ring and Ring 2, once again played by Hitomi Sato.
The mark of the curse is seen as 4 lines on the arm (when Mayu Akikawa wakes up from her nightmare). In another part of the film, the arson crime scene of the apartment complex had taken place on the 9th floor. In Japan and some Asian countries, the number 4 and any number containing the digit 4 is considered an unlucky number and is associated with death (due to the words 4 and death sounding similar in their native languages). The fear of the number 4 is known as tetraphobia and is taken seriously in some Asian countries that sometimes the number 4 is avoided in homes, hospitals, businesses and other properties. The number 9 is feared in Japan as the number for "suffering" because it sounds similar to the Japanese word for suffering or torture. When written, this sound means pain. Usually, this number is purposefully muttered when someone wants to make a threat or curse. Like number 4, buildings often skip the number 9 when numbering their rooms or floors, as it is believed to bring negative energy and unfortunate events.
The film is supposedly based off of the novel "Tide," the last book in the Ring book series by Koji Suzuki.