The director & writer gave us the backstories like puzzles with pieces all over the movie and it's upto us to piece them together and this is how I put them together.
I wrote this in parts so u can jump to the part u want to read.
Jin Soo & Cheong Seok
Let's start with Jin Soo and Cheong Seok's storyline first. Cheong tells Jinsoo that he seems familiar for some reason, that's because Cheong saw him at his mother's funeral. Cheong's Mother killed Jinsoo's wife and child in a drunk drive accident. But she got lenient sentence in the court which enraged Jinsoo causing trouble in the court and hence his record of disturbance which cop finds during his background check. Cheong's Mother couldn't get through the guilt and commits suicide. She apolozises to Jinsoo and asks him to take care of Cheong. Thus Jinsoo meets Cheong at the funeral. Jinsoo takes Cheong to temple and becomes a Monk where he meets his fate as guard of Sarira Casket and his duty to ascend the souls. Even though he became a Monk he couldn't get over his hate and wanted to kill Cheong as payback for his mother's sin but couldn't do it, so he leaves the temple ( this is mentioned by the monster at the end). He becomes a construction worker but the souls still follow him asking him to ascend them. After the final stepping stone The monster needs to possess him cuz he is the guard who can open the Sarira Casket.
The Monster
According to ancient scriptures in India, the difference between animals and humans is the intelligence. But unfortunately humans suffer because of their own intelligence. Our intelligence has two parts Memory and Imagination. Although they are a blessing, some times we suffer because of them. We suffer because of something happened in the past(memory) & we suffer because of what may happen in the future (imagination). even though it's not happening in the present, we suffer because of Past and Future.That's why Buddha said the the key is to let go. The two eyes of the monster represents these two sufferings. The red eye needs to go through 7 stepping stones to reach the black eye.
7 stepping stones
The primary characteristics of 7 stepping stones is that they tried to kill themselves but failed. The 7th stepping stone is virgin shaman and she is different from others. While other stepping stones are regular people who are oblivious and sitting ducks, she is a shaman who can sense things. So why would she sit put when a monster is coming for her? Obviously she would know ways to hide and protect herself. Remember the talisman she gave to the cop protected him temporarily. Although she can't evade the monster forever, she can evade him temporarily and that's all she needs to do as the monster has only limited amount of time(8days). That's where the Red maid comes in.
Ae Ran / Red Maid
Red maid means maid of the red eye, hence she is chained to the red eye. Red on her white clothes is symbolic. Her duty is to assist the monster.
Ae Ran was an abused child. The archeologist saves her and adopts her, thus he became her father and she lived happily until everyone accused her father of forgery which broke him. He became obsessed with proving that he was not a fraud. He wanted to prove by bringing out the monster from the Sarira Casket which everyone called fake. He tells Ae Ran that he needs a Maid as a sacrificial offering while reading the writings on the stone tablet which reads " The one who bewitches the virgin & stall her, the Red maid" which means the monster needs the maid to keep the virgin shaman from running away until he comes. The archeologist asks Ae Ran if she thinks he is crazy, even if no-one believes him, she should believe him. she says if it's something someone u love said, u always want to believe it no matter how foolish it is. She decides to sacrifice herself and become the Maid to help her father. Now you may think why she took this extreme step, archeologist is the first stepping stone which means he also tried to kill himself in the past, that's why she wanted to help him desperately at the cost of herself. So she becomes the maid chained to the Monster. Once the virgin shaman comes to the meditation group like other stepping stones, she follows her to keep her from running away until the monster came for her. (In the scene where the cop visited the shaman, she tells him that the girl kept her there so she couldn't run away). But while staying with her and sharing her story, Ae Ran must have wanted to help the shaman, so she told her a way to save herself which is by finding a person with the same Natal chart as the shaman and offering his blood as alternative to the Monster, that's where the young cop Dong Jin comes in. When he came for the talisman shaman took his blood in a small cup. When the monster first came to her house and looked through the hole in the door, Ae Ran offered Dong Jin 's blood in the cup as alternative, doing this is equivalent to the archeologist offering blood at the beginning. The monster smelled the blood and left for the school girl. When Jinsoo came kill the shaman, her face was covered with talisman cuz she was hiding from the monster. When monster (in the school girl) smelled Dong Jin, it recognizes his blood and takes him as the alternative to shaman cuz the time is running out. Thus Ae Ran helped shaman from monster. Even though Ae Ran left with Cheong, she is still chained to the monster as a servant. which is why at the end, when monster calls his maid to find Cheong, she had to take off Cheong's protective clothing.
At end of movie , Cheong was able to free AeRan from her chains because he now became the successor of Jinsoo as the guard of the Sarira casket. Now with AeRan by his side, the next potential Bring it on Ghost story starts....
just kidding, now its Cheong's duty to ascend the souls like Jinsoo and AeRan would be the first soul he ascends.....or not he might fight ghosts with her it's upto u to imagine ; D
