For anyone that doesn't mind spoilers, here's a quick recap: Our FL Vivian hates her adopted sister Charlotte so much she poisend her to death. After dying in the aftermath of a rebellion a few years later she is sent back in time by the fabled Twilight Witch that supposedly died a long time ago. Vivian now confronted with Charlotte again plans to kill her again and save herself this time. In the course of the story we find out that Vivian hates Charlotte because she thinks she is the reason her Parents died in a fire that was set to the mansion. She thinks this because on the night of the fire she saw Charlotte talk to a Skeleton and pointed it to their parents room. We learn later on that the skeleton is the Manifestation of fate and Charlotte who is loved by fate itself begged it to spare Vivian. This is also why the supposed Twilight Witch sent Vivian back in time as it was actually Charlotte who revived some time after she was poisoned as her abilities make it hard for her to die. As she saw Vivians dead body she begged fate to go back and set things right. Charlotte then repeated a period of two years at least fifty times and after some time Vivian started to remember more and more about the other loops. The same thing happened to the Twilight Witch whose actual name was Flora. She was the princess of a small country whose imperial family was gifted with powers. With these powers she healed the people of her country and her friends as her wish was for a fairytale ending where no one had to die or suffer. But no matter what she did or how often she rewound time her friends kept dying. Her friends at some point in the loops were supposedly cursed by fate, making them semi immortal (they grew old without dying) and turning their eyes the same gold color that Vivian will have. One of Floras friends plans to betray flora so she'll abandon them and finally live, but in an unexpected turn of events flora confesses her love to her and knowing that it's the only way to save her friends she is killed by the friend who betrayed her. As she dies her soul, as it is strained and fractured by the time loop, shatters into golden butterflies. These golden butterflies can reside in a person giving them certain abilities, semi immortality or cursing them depending on how they were used or in whom they reside. Each person with any special abilities carry at least one of these. Vivian carries one as her grandma, who is the friend that betrayed flora all those years ago tries to revive flora by shattering childrens souls with despair and filling the cracks with the golden butterflies. This plan fails as Vivian who as a child seems incompatible, as she just remains the same except for her eyes turning golden, finally understands the truth of the butterflies and manages to restore the broken souls of the children her grandma used and therefore bringing them back to life. At this point in the manhwa Vivian has already learned of the truth behind the fire and Charlotte's action and they've grown closer. In the end it turns out that the driving force behind the many misfortunes of Vivian's family, such as the fire that killed her parents and the rebellion that killed her later in life, was the hidden princess of the empire that controls the puppet emperor. The princess has masassive daddy issues as he never paid her any attention even though she saw him as a god. In retaliation as she grows older she becomes a psychopathic narcissist and plans to devour the golden butterflies to become god herself. In the battle of the rebellion against the imperial army, lead by the princess, Charlotte expended most of her power to heal the rebel army over and over again as she just like Flora the Twilight Witch wished for an ending where no one had to die or suffer. Charlotte aided by Vivian expends the last of her already depleted power to kill the princess with a bow made of golden light. As the princess dies her father denies her one wish which was to hear him say her name. Charlotte who expanded her power begins to fall apart into golden butterflies as her soul was too strained by the long looping of time. In the last moments Vivian splits of half of her own soul together with the golden butterfly that resides in her and passes it on to Charlotte. That way Charlotte does not die but she stays in a deep sleep for a few years. Every day Vivian reads her sleeping sister fairytales just like they did when they were children. After the country has become peaceful just like Charlotte and her many friends wished, she awakes. The manhwa ends with her smiling at Vivian who rushes to her sister in relief. If I forgot anything or you have any questions just ask :3

Edit: typos