Episode 6 of "If Wishes Could Kill" takes us back to the year everything began. As Chae-yoon mentions, it all started with Hye-rung and Si-won. The episode opens with Hye-rung dropping by Si-won's house to seek her out. Si-won's mother, the shaman Eob-soon, notices that Hye-rung has a cursed splinter in her eye. Using her shamanistic powers, Eob-soon heals her. Hye-rung is touched and curious, despite Si-won's many warnings to stay away from Eob-soon.
It turns out that Si-won even ran from home to avoid her mom. She blames her mother's alcoholism and her job as a shaman for her father's death. She's not pleased when Hye-rung mentions that she dropped by her house. On their way from the hideout, they end up late for the bus because Hye-rung is too lovestruck to take the same bus as her crush, Gi-tae. Si-won promises to keep Hye-rung's crush a secret as long as she keeps her secret. Si-won doesn't want anyone to know she's the daughter of the shaman.
At school, Hye-rung expresses her interest in joining the coding club, but Si-won subtly suggests that she may not be suited for it. Hee-jin asks Si-won to team up with her, Gi-tae, and Dong-jae to sign up for the app contest. As Si-won starts spending more time with her coding friends to work on the app, Hye-rung starts to feel alienated. At the same time, Si-won lets them think that Hye-rung is the odd daughter of the shaman. Dong-jie suggests they take inspiration from the shaman and make an app that fulfills wishes. Si-won ends up doing most of the work.
Outside school, Si-won avoids her mom when Hye-rung unfortunately keeps meeting Eob-soon. Ultimately, her curiosity gets the best of her, and she takes up Eob-soon's invitation to visit. Eob-soon tells her about her job as a shaman and claims that only someone with an innate gift can do it.
When Si-won discovers them, she is filled with anger. Hye-rung tries her best to apologize, but Si-won refuses to forgive her. She believes that Hye-rung is faking their friendship and looking for evidence to blackmail her.
Later, at the hideout, Si-won finally forgives Hye-rung and reveals the coding she is doing for the app. She expresses a wish to use the saju method to wish for her mother's death and asks Hye-rung what her wish would be. Hye-rung admits that she would want Gi-tae to fall in love with her.
To test the app, Si-won convinces Hye-rung to make a video earnestly wishing for Gi-tae to fall for her. That night, Si-won opens up more about her mother.
The following day, on their way to the hideout, they witness Eob-soon fighting with the convenience store lady, demanding alcohol. Si-won is embarrassed and walks away. She heads home and destroys the shrines. Eob-soon sees her leaving and doesn't realize what has happened until she gets inside. Unfortunately, Si-won has angered the spirits by defiling their altar. She performs multiple rituals to save Si-won's life, which work, but Eob-soon's strength is waning as she starts bleeding.
The following morning, Hye-rung drops by the house since Si-won had mentioned she would sleep there. Hye-rung sees a bloody Eob-soon performing a ritual at the back of the house. Eob-soon begs her to put a talisman in Si-won's pocket without her knowing, insisting that it is the only way to save Si-won's life.
Hye-rung is conflicted and decides to fulfil Eob-soon's request. However, when Si-won and Hee-jin walk in on her, Si-won is angry and slaps her hard. She tears up the talisman and, without a word, ends her relationship with Hye-rung.
Hee-ji is shocked by the fight and tells the rest of the team about it. Si-won overhears them judging her and Hye-rung and is offended when Dong-jae asks if maybe she is the real daughter of the shaman. She storms inside the room and shows them the app. She then reminds Gi-tae that he didn't help and asks him for a favor. They use the app to expose Hye-rung's crush on Gi-tae, causing Si-won to publicly embarrass and physically beat Hye-rung.
In retaliation, Hye-rung performs a ritual just as Eob-soon had taught her. She makes a cursed deolmi using Gi-tae's and Si-won's personal items and makes her wish, which results in Gi-tae slitting his throat on the streets.
As for Hye-rung, she tries to stop the app by shutting it down from the main server after learning of Hye-rung's death. By this point, it is too late; the server won't go off. She ends up slitting her throat in the media room, trying to fight back and slicing her face before finally dying with a repeating wish for Hye-rung's downfall.
