WARNING: The further text contains SPOILERS, so it's highly recommended to watch the movie "Sadako 3D" before reading this text!
„Sadako 3D" is the newest sequel of the Japanese „Ring" series. If it is seen by a person who doesn't know anything about the basic „Ring" story, the movie will be partially confusing to them. But someone who did watch the previous „Ring" movies will be even more confused if they haven't read the novels by Koji Suzuki, the writer who invented the basic „Ring" story. Understanding the movie „Sadako 3D" requires a high knowledge of the entire „Ring" universe, not only of the movies, but also of the novels, the skill of analysing and inductive reasoning, and even a bit of imagination, since Suzuki's novel „S", that this movie was based on, hasn't been translated from Japanese yet.
Although this movie follows Akane Ayukawa as the protagonist, the impeller of the story is Seiji Kashiwada. Although it was never clearly said in the movie, it makes us think that he was born with supernatural powers, which is why the society declared him a freak and abandoned him. We come to that conclusion based on three clear facts. The first fact is that in his cursed video, he mentions the revenge on the people who abandoned him. The second fact is that Akane Ayukawa was also born with supernatural powers, which is why she was bullied and abandoned by her classmates, which is why she almost committed suicide. Since it's obvious that Akane and Kashiwada were of more-or-less the same age, we can assume that the people around them had similar mentalities and that Kashiwada was also abandoned due to his supernatural powers. The third fact is that Kashiwada somehow (it was not directly explained how) managed to get in touch with the spirit of Sadako Yamamura and to make his own cursed video. Some watchers would say that this conclusion is wrong, that by mentioning people who abandoned him Kashiwada was actually referring to those people on the internet who talked his artwork down. But I think that what those people did to him was some kind of a trigger that made him decide to take a revenge. The fact that he had supernatural powers is undeniable, because otherwise he wouldn't be able to do everything he obviously did.
Holding a grudge against the entire human race, and wanting to take the revenge on those who abandoned him, Kashiwada wanted to exterminate the mankind. We can assume that one of his supernatural powers was communicating with spirits. With his extremely powerful grudge, similar to the grudge of Sadako Yamamura, he attracted her spirit and she got in contact with him. That's how he found out about her existence. He found out that she would be capable of exterminating the mankind, so he started abducting girls with long black hair, dressing them in white night dresses and throwing them in the same well where Sadako had died. But, in order to come back to life, Sadako needed a medium, a special person with particular supernatural powers. In order to find that medium, Sadako needs to be able to manifest herself to random people, and for that she needs a video. Here comes the problem that may confuse all the fans of „Ring" movies, if they haven't read Suzuki's novels.
The first „Ring" movie had two sequels, „Spiral" and „Ring 2", and those two contradict each other. It's obvious that „Sadako 3D" is a sequel to „Spiral", not to „Ring 2". We know that because here we have Takanori Ando, the son of Mitsuo Ando who was the protagonist of „Spiral". But here comes the question, what happened to the famous cursed videotape? Why can't Sadako manifest herself to people via that tape? The answer is contained in Suzuki's novel „Loop" and the story „Happy Birthday", although none of those two has been adapted into a movie. „Sadako 3D" nowhere mentions Ryuji Takayama, a very important character in those two stories. Takayama is crucial for the understanding of this movie. In „Loop", we find out that the entire story of the novels „Ring" and „Spiral", just like all the „Ring" movies, happened in a virtual reality named Loop. After dying in Loop, as a victim of the deadly videotape, Ryuji Takayama was cloned by a scientist in the real world (out of Loop). He was reborn as a new child named Kaoru Futami, and he lived his first 20 years without knowing anything about his past life in the virtual reality. But under particular circumstances, Kaoru finds out about Loop and about the deceased Takayama whose genes are identical to his own ones. To save the world from an apocalyptic virus that he accidentally brought with himself to the real world, Kaoru is forced to return to Loop as Ryuji Takayama. After his return, he finds a vaccine for the so called Ring Virus, which is spontaneously generated in the people who watch the cursed video and die of that virus seven days later. As the vaccine is discovered, the videotape becomes harmless. Furthermore, Takayama manages to produce a virus that attacks Sadako and her clones (which are well explained in the novel and the movie „Spiral"). But since he was also reborn in Loop (helped by the people from the real world) from Sadako's womb, Takayama is also destroyed by his own virus.
But Seiji Kashiwada seems to be Sadako's new chance to come back to life. Since she can't manifest herself to the people via her old cursed video, she makes a deal with him. Since his cursed video shows his own death, before which he mentions revenge, we find out that he cared about the revenge more than about his own life, so he was willing to sacrifice himself. In the movie we clearly see that he filmed the video with his iPhone and that the person who killed him was Sadako Yamamura. From the earlier movies we know that the victims of Sadako's tape see Sadako emerging out of a screen before they die, if there is a screen around. When the police inspector Koiso studies the room where Kashiwada's death was filmed, he says that the room seems to be fake, set precisely for filming that video, that it didn't exist in that same form earlier and that there is something missing in the room. What is missing? Technological devices like a TV set or any other device with a graphic screen, THAT is missing. In the moment of Kashiwada's death, the only device with a graphic screen was his own iPhone. According to those facts, we can assume that Kashiwada watched Sadako's old cursed video and didn't take the vaccine against the Ring Virus. Since he had a deal with Sadako's spirit, he could have known the exact moment when he was going to die. Seven days later, knowing it was the moment of his death, he was sitting in that room where the only device with a screen was his iPhone. That is why Sadako emerged out of his iPhone, which was filming a video at that moment. The iPhone filmed the moment of Kashiwada's death, and the recording was broadcasted live on the website of Nico Animations. The movie lets us know that Kashiwada was very intelligent, so it's possible that he hacked the website to enable the livestream for his own video. Since the iPhone filmed Sadako's manifestation from itself, just like it filmed Kashiwada's death caused by it, that video was cursed. But although the video, after being broadcasted live, was deleted from the website, due to it's paranormal origin it had it's own will and the ability of travelling through the internet. So, as we see in the movie, the video was showing itself to randomly chosen people who were online in that moment. If the video shows itself to a person who is not the medium seeked by Sadako, the person is killed and their death looks like a suicide.
But the movie makes us think that Sadako and Kashiwada actually had different intentions, or at least a different perception of the idea of Sadako's resurrection. In the room where Kashiwada's death was filmed, officer Koiso discovers a picture of a monstrous Sadako, with long spider-like legs. Not long afterwards, in presence of the person who IS the medium seeked by Sadako, the corpses of the girls thrown by Kashiwada into the well are transformed into monsters like the one discovered in Kashiwada's death room. According to all those facts, we inductively come to two conclusions. The first one is that Kashiwada, by mentioning the resurrection of Sadako, was actually referring to those monstrous creatures that can exterminate the mankind. The second conclusion is that one of Kashiwada's supernatural powers was thoughtography (which is how he „painted" the monstrous Sadako on the wall), the same power that Sadako Yamamura had.
We have deduced that, in order to bring those monsters to life, the medium person was needed to come close to the well. As he was able to communicate with Sadako's spirit, Kashiwada was aware of that fact. It was obviously clear to him that the medium person will get close to the well only if he/she feels it necessary to INVESTIGATE. So, he needed his death to become the object of an investigation. That's why, in agreement with him, Sadako made his body disappear. We saw a scene where Sadako physically sucks Takanori Ando into a screen. According to that, we can assume that she also sucked Kashiwada's body into his iPhone. That is how Kashiwada's death became an intriguing object of an investigation, which was what, as we have deduced, Kashiwada wanted. Let's assume that, after everything what happened, Sadako had a physical control over that iPhone. Influenced by her will, the iPhone was moved to the house where Sadako had grown up, next to the well.
The medium that Sadako was looking for is no more or less than the protagonist of the movie, Akane Ayukawa. As we know from the movie, Akane was also born with supernatural powers. As she was in the right place at the right time, when Sadako tried to kill Lisa Kitayama, a student who had previously watched Kashiwada's cursed video, Sadako recognizes Akane as her medium and she starts to attack her from everywhere. In one scene we clearly see that Sadako tries to merge herself with Akane's body, after Akane finds Kashiwada's iPhone and gets sucked inside. That makes us deduce that Sadako wanted to make Akane find that iPhone, which became the core of her power after Kashiwada's death. In order to make Akane find the iPhone, Sadako abducts Akane's boyfriend Takanori, and he is imprisoned in Kashiwada's iPhone. Soon afterwards, Akane encounters Takanori's friend Enoki, who laughs at her and says that Takanori is going to die if she doesn't look for him. As in one moment Enoki appears deformed, we realise that he is actually a ghost, that he was also killed by Kashiwada's video, and that Sadako used him as a trap, to make Akane find her house, and the iPhone. With the officer Koiso, Akane visits that house. As she is the medium that Sadako was looking for, when she comes close to the well, the dead girls are transformed into living monsters that start to climb out of the well. The first one of those monsters kills the officer immediately. Trying to escape from them, Akane enters the house. When her fear becomes strong enough, her scream (from earlier we know that her scream can be destructive in a critical moment) disintegrates all the monsters. But then she finds Kashiwada's iPhone and Sadako sucks her in. As she has her medium and considers her resurrection a fact, she accepts to set Takanori free. She probably did it to calm Akane's strong negative emotions down, to make it easier for herself to possess Akane's body. But, after Sadako merges with her body, Akane's soul is struggling to resist and the two of them fight inside the body. Meanwhile, the freed Takanori wakes up out of the iPhone and he hears Akane's scream, so he smashes the iPhone with a rock. Akane is set free.
But there are some more questions that can bother the watchers. First question: What happened to the resort that was built above the well, as we saw in the first „Ring" movie? Why is it not there anymore? The answer: in the novel/movie „Spiral", Asakawa's journal (containing the information of all his investigations) was published as a novel, so many people found out what was there under the resort, so they didn't want to go there. That is why the resort became useless and it was taken down, but probably no one wanted to mess up with the well, so it was left there. It's quite obvious that no one was visiting that place. Otherwise, Kashiwada surely wouldn't dare to go there so often to throw women down the well. Second question: What's the point of the butterflies? The answer: As we see those butterflies in Sadako's house, and in the well too, we deduce that the forest around the well is their natural habitat. Kashiwada probably saw many of those butterflies while he was visiting that place, sewing the white dresses there, putting them on girls and throwing the girls down the well. In the scene when the officer Koiso visits Kashiwada's death room and touches the wallpaper, the wallpaper is (influenced by Kashiwada's spirit) disintegrated into a bunch of butterflies that fly away, revealing the thoughtograph of a monstrous Sadako. As we already know, Kashiwada's intention was to create those monsters to exterminate the mankind. But independently of his intentions, Sadako had her own plan, the plan of coming back to life in the body of Akane Ayukawa, her medium. Kashiwada didn't know that the medium was going to be a person whose scream can destroy all his monsters. But Sadako did notice that, so she didn't interfere with Kashiwada's plan. Third question: Why did the officer Koiso see Kashiwada's spirit who told him that Sadako was completely resurrected, even before it really happened? The answer: he said that because he knew that Sadako found her medium, who will accidentally bring his monsters to life when she gets close to the well. As Takanori was abducted, Kashiwada knew that Akane was going to look for him, and that it would be easier for her to find the well if she accompanies the officer Koiso, which is why he showed himself to the officer. Fourth question: Why do all those monster transform into a bunch of butterflies after their death? The answer: As Kashiwada had supernatural powers and an extremely powerful rage, we assume that a lot of his negative energy was left in the well, which he was visiting very often to throw the girls into it. That negative energy contained his thoughts about the butterflies, which were obviously common there and thus attracted his attention somehow (maybe he was annoyed by them, and the annoyance increased his negative energy). It was similar with Sadako. After she died in that well, her negative energy was left there, and that negative energy contained her thoughts which were in a particular moment projected onto the videotape. In the presence of Akane as the medium, Kashiwada's negative energy brought the corpses to life in that monstrous form. After their destruction, the monsters were disintegrated into no more or less than Kashiwada's thoughts that influenced their formation, thus the butterflies. That plenty of butterflies was probably attracting his attention whenever he would visit that place to throw a girl into the well. Last question: What did Kashiwada's landlady mean when she said:"Isn't it all artificial?"? The answer: She was referring to the fact that they all lived in Loop, which is a virtual reality. How did she know that? In Suzuki's novels we find out that Sadako personally knew Ryuji Takayama, who was brought back to Loop from the real world. So, Sadako learned about the virtuality of her world from Takayama, and in some occasion her spirit told Kashiwada about that. In the movie, the landlady says that she had some nice conversations with Kashiwada, she actually liked him. Obviously, Kashiwada told her about Loop. She probably didn't take it seriously, but she found that theory quite amusing and interesting, which is why she was saying that.
According to this entire text, we find out that the movie „Sadako 3D", although it apparently misfits the rest of the „Ring" universe, can be explained in terms acceptable for the „Ring" stories. Anyway, the fact that the movie requires such a detailed analysis and the knowledge of the stories (which weren't adapted into movies) to be understood, is a downside to it. But after all, we are waiting for the translation of Suzuki's novel „S", that might eventually confirm or deny this theory.