Great movie. Require some brain cells to understand it?

MAIN CHARACTERS:
Cheong seok(Ml lead)
Ae ran(Fl lead/Red maid)
Seon hwa(Monk)
Dong jin(cop)

STORY:
The story starts with a man telling a story of Buddha and demon's eyes that Buddha seperated those eyes(black and red) from each other one in east and one in west.In movie one is present in Desert ?️ and other was present in a temple under protection of Monks where Cheong seok(Ml lead)was present at start of movie. These eyes were seperated by Buddha but they can again meet in future and cause disasters on earth. There is procedure of awakening of eyes and meeting again which is 7 stepping stone. Then a archaeologist trying to prove that, this Legend is true and the eye that was hidden in the desert?️ (the red one), he found it. He told the people that what I said to you was really true. Look i found it but no one believes him.He wants to prove it desperately. So He used blood of seven people for awakening red eye. After awakening, the red eye have to pass 7 stepping stones to reach the black eye.
The monks didn't know the all stepping stones among 7 except last one which is VIRGIN SHAMAN. They wanted to kill her so that both eyes can't meet and prevent disaster .

Seon Hwa(monk) And Cheong Seok(ml Lead):
Cheong seok was sent to seon hwa by the monk present at temple to inform him that Demon is coming. Cheong seok said to him (seon hwa) that he seems fimiliar to him he don't know the reason but yes he met him at funeral of her mom.His mom cause car accident because she was drunken. During this accident, two people died which is the family of Seon Hwa(monk) his daughter and wife. Cheong seok's mom was given sentence. But seon hwa was not happy why she was not given life sentence so he cause disturbance in court which the detective mention. But Cheong's mother could not get through the guilt and commit suicide and asked Seon hwa to protect her child but he wanted to kill him as payback but couldn't do so. Then, he left the temple and started working at construction sites. When he left the temple the duty was given to him to guard Sarira casket transferred to Cheong seok.

7 STEPPING STONES & Dong jin:
The blood used are of people who tried to commit suicide but survived. The eye moves from person to other by hiding in their bodies by recognizing the smell of blood (The eye can smell the blood of all 7 people because it was used in its awakening)and reaches the door of VIRGIN SHAMAN but she use the blood of dong jin(cop) as alternate of her when he came to her for talisman as he was not the part of stepping stones but red eye used him as last step when Shaman was not present there at 8th day (demon has limited time of 8 days). Dong jin also once tried to commit suicide that's way the eye find him suitable.

Ae ran:
So many of viewers were confused what the role of Fl lead exactly i was also confused. it's difficult part?.
So, the role of Ae ran was guarding the Virgin shaman so she can't run away anywhere. As we know she was abused by others so one day a man adopted her. Yes that man was archaeologist who started all of these. Her foster father. He said he needs someone to sacrifice, so she agree because he saved her from the abusers.She sacrificed her and became the maid of demon and started to serve him by chasing Virgin shaman. But with the passage of time she became close with shaman and she told her that she can saved her from the eye and she told her the way which was the using of dong jin's blood.
As she was maid of demon so at the last of movie when demon ordered her and she take the jacket off from cheong seok which he was wearing for his protection.
Hope u like it?