Ae Rin is a humble high school student who is often bullied by her classmates. However, unknown to them, behind closed doors, she is a highly popular online influencer. At home, she dresses up, applies makeup, takes photos of herself, and then uses Photoshop to transform into a completely different person—a conventionally attractive girl with an Instagram account named Genie. She has many followers and receives support on Instagram, with brands sending her products and money to promote them. Yet at school, she remains friendless and is frequently bullied by a classmate named Ha Neul. Her only friend is Jin Seong, a fellow student from a different class who is training to join an entertainment company. Due to his training, Jin Seong doesn’t have real friends at school; people only approach him to ask about other idols. He often retreats to the rooftop to hide, where he meets and befriends Ae Rin. Jin Seong tells her she is as pretty as a famous actress, which makes her extremely happy. The next day, Jin Seong invites her to lunch, but as she is about to leave, her parents stop her, saying they have plans to eat together, which Ae Rin disdainfully rejects. During her date with Jin Seong, Ae Rin enjoys herself but also has another task: to counter online criticism claiming Genie only takes indoor photos and that all her pictures are edited, challenging her to take outdoor photos. She uses the excuse of needing to return home to says bye to Jin Seong. She goes to a coffee shop, takes some photos, then goes home to edit and publish them, dismissing doubts that she is a fraud. One of her fans, particularly concerned for Genie, messages her to check in and suggests meeting up in real life, but Ae Rin excuses herself, claiming she has a phobia of crowds and must limit her outings. As Ae Rin is about to go to sleep, a stranger messages her, saying he saw her outside and sends a video of Ae Rin at the coffee shop. Ae Rin is terrified that someone has discovered her secret. The next day, Ae Rin wakes up after a nightmare and also receives a new message from a stranger under the account name "the cool guy." At school, he keeps texting her, and Ae Rin feels unwell, to the point that she doesn't even care about Ha Neul and her friends bullying her as usual. Terrified because it seems like "the cool guy" knows her, she faints during P.E. class. Jin Seong, passing by at the time, takes her to the nurse's office. Meanwhile, the homeroom teacher believes Ae Rin fainted due to Ha Neul's bullying and threatens to call Ha Neul’s parents if it doesn't stop. Ae Rin becomes paranoid about the possibility of her identity being revealed, worrying that even Jin Seong would not want to be friends with her anymore, and of course, her classmates would have even more reason to ridicule her. However, things don't turn out as bad as she fears; Ha Neul writes an apology on a piece of paper and throws it to Ae Rin. Jin Seong increasingly shows that he likes Ae Rin. But these events don’t alleviate Ae Rin’s worries about "the cool guy" knowing her secret and possibly exposing her at any moment. That week, Ae Rin dares not post any photos or updates. Her followers become very concerned, and brands urge her to post and threaten to terminate their contracts. Left with no choice, Ae Rin posts a photo, and "the cool guy" starts to blackmail her more intensely. He arranges to meet her at the school's lounge after hours. However, when Ae Rin waits, only Jin Seong shows up. Ae Rin suspects that Jin Seong is the one threatening her, but he says he just wanted to walk home with her and had been looking for her everywhere. Ae Rin tells him to leave, but Jin Seong stays sitting in the schoolyard waiting for her. As Ae Rin messages "the cool guy," she notices Jin Seong also checking his phone. She doesn’t know what to think; Jin Seong seems very much like "the cool guy," yet he has always been kind and cheerful towards her, making her afraid that he might be toying her. A flashback shows that Ae Rin moved to the school a few months ago and noticed Jin Seong eating alone at the canteen. They then became friends on the rooftop when both went there for some fresh air.

Back in the present, Ae Rin is panicked at the thought that her only friend at school might be the person who is blackmailing her. At that moment, the school guard arrives and tells her to go home.

As Ae Rin walks down the corridor to leave the school, Jin Seong startles her again. He insists on walking her home. Along the way, they hear a cat meowing, and Jin Seong runs over to feed it, mentioning that he loves cats. Coincidentally, "the cool guy" account had also posted cat pictures, and Ae Rin becomes full of paranoia again, thinking Jin Seong might be "the cool guy."

Ae Rin uses this as an excuse to run all the way home and cries out of disappointment, unable to believe that the person she secretly likes is playing games with her.

Meanwhile, Ae Rin's parents are also worried about her state, especially her father. Her mother seems to be hiding something.

At the same time, Ae Rin realizes that she had used the Genie account to like his pictures, and he had also followed and liked Genie's photos back.

The next day on the rooftop, Jin Seong tells Ae Rin about this. To confirm her suspicions, Ae Rin messages "the cool guy," but Jin Seong does not react; he says his phone had been confiscated by a teacher.

However, when Ae Rin returns to class, "the cool guy" messages her again as usual, this time demanding she wear red lipstick to school or he will expose her identity.

Driven mad by this threat but having no other choice, Ae Rin complies and wears red lipstick to school the next day, quickly getting spotted and teased by Ha Neul and her friends.

The teacher enters the class and stops the bullying but also tells Ae Rin to wipe off the lipstick. Ae Rin even contemplates suicide but stops herself in time. That day, due to an electrical issue, classes end earlier than usual.

On the bus home, Ae Rin sees that "the cool guy" has posted a photo on his account taken just minutes earlier as she waited for the bus, signaling to her. Ae Rin returns to the bus stop and follows the trail of photos he continuously posts.

Finally, they lead Ae Rin to a house. "The cool guy" then sends Ae Rin a CCTV video showing her flustered in front of the house. Realizing this seems to be the house of the blackmailer, Ae Rin tries to run but it's too late; the gate suddenly slams in her face.

At the same time, a young man enters, and it's not Jin Seong but someone Ae Rin never expected: Kim Ho In, the class president of the class Ae Rin is in.

It all started when Jin Seong posted a photo of himself in uniform online; although Ae Rin quickly deleted it realizing it could lead back to her, many had already screenshotted and reposted it.

Ho In, curious, had narrowed down his search, initially thinking Ha Neul seemed like the most likely person to be Genie. However, he later realized that all the designer items she was using were stolen from Ae Rin, plus when he was tasked by a teacher with confiscating students' phones during an exam, he noticed that Ae Rin's phone was receiving numerous notifications from Instagram, and at that point, he had his answer. He seems quite pleased to have caught Ae Rin off guard. Directly, Ae Rin asks Ho In what he truly wants and kneels to beg him for mercy. However, Ho In is quite a psychopath and simply enjoys the fact that he is now the only one who knows Ae Rin’s secret.

Meanwhile, Ha Neul is getting ready to go on a date with Ho In. It turns out that Ha Neul is the secret loyal fan who has been talking with Ae Rin since she started the Genie account. Ha Neul probably cannot imagine that the person she admires and has been talking closely with is actually the classmate she bullies every day.

The next day, Ho In takes Ae Rin to a café owned by an acquaintance and creates an opportunity for her to take more attractive photos. However, Ae Rin still reminds herself to be cautious around this unpredictable person. When Ae Rin shows suspicion, Ho In removes his shirt and shows her a scar on his shoulder, saying they are not enemies. Ae Rin quickly takes out her phone and snaps a photo, wanting to hold onto something that could be Ho In’s weakness.

Although they still harbor suspicions about each other, Ho In offers to take pictures for Ae Rin and goes to buy coffee for both of them. During this process, Ho In starts to develop feelings for Ae Rin, and this causes him to neglect his girlfriend, Ha Neul.

That evening, Ha Neul is very upset and messages Ae Rin, blaming herself for not being pretty enough to fully capture her boyfriend’s affection. Ae Rin realizes that everyone has their insecurities, even a bully like Ha Neul.

As Ae Rin is about to go to sleep, she receives a message from Jin Seong on the Genie account. Ae Rin replies to the message but is disappointed to see that he seems to be hitting on Genie, the pretty girl she created. All this time she thought Jin Seong liked her as Ae Rin, but it turns out he is just like everyone else.

To confirm her suspicions, Ae Rin daringly flirts back with Jin Seong to see his reaction. The next day, Jin Seong calls Ae Rin and comes to her class to invite her to the rooftop, but she completely ignores him.

It turns out that the night before, Ae Rin used the Genie account to tell Jin Seong to send her a seductive video if he was interested, and he actually sent one. Ae Rin does not want to watch it but can guess its content, which disappoints her further. Therefore, she ignores Jin Seong.

In the evening, when she returns home from school, Jin Seong waits outside her house to ask what happened. Ae Rin says nothing and simply tells him to leave. At home, Ae Rin's mom tries to talk to her and tells her to take some vitamins, but she refuses and runs to her room. At midnight, she goes out and sees Jin Seong still waiting for her. Ae Rin mentions Genie, but Jin Seong doesn’t seem to know anything about what she’s saying. Ae Rin gives him some harsh words and tells him to stop acting like he likes her when he does not. Jin Seong informs her that he will soon debut and will have to leave school, and that's why he wanted to talk to her.

Ae Rin is sad and uses the Genie account to message Ha Neul to share her feelings. Ha Neul is also sad because Ho In is not paying attention to her and is ignoring her.

The next day, Jin Seong says goodbye to his class, but they don’t seem very emotional. He also leaves a gift and an early birthday card for Ae Rin on the rooftop, where they used to spend time together. Ae Rin is very sad to see Jin Seong leaving the schoolyard but only cries and does not chase after him.

Meanwhile, Ha Neul is completely ignored by her boyfriend Ho In and decides to start exercising because she thinks she is being ignored for not being pretty enough. It turns out Ha Neul comes from a poor background, living with her hardworking mother. When checking Ho In’s messaging app account, she discovers that he has a new profile picture of him at the café where he was with Ae Rin. The next day in class, Ha Neul dreams about the truth being exposed that she lives in a poor family. She becomes increasingly self-conscious about her appearance and even wears a wig, yet Ho In pays no attention to her. He goes to the rooftop and has a snack with Ae Rin. Ha Neul follows him and sees that they are happily playing together, which infuriates her and she uses it as an excuse to bully Ae Rin in class. She even lifts Ae Rin's skirt so that everyone can see and humiliate Ae Rin. Ae Rin goes to the restroom crying and decides to block Ha Neul from her Genie account. A flashback reveals that the reason Ae Rin transferred to the new class was to meet her loyal fan, Ha Neul. Seeing that Ha Neul likes the watch she is wearing, Ae Rin gifts it to her, and Ha Neul is very moved. That evening, Ae Rin and her parents eat at a small restaurant where Ha Neul’s mother works, and Ha Neul is there helping her mother. Ha Neul worries that Ae Rin will reveal this to everyone in class, but Ae Rin assures her she will not do so and also tells Ha Neul that her current father is her stepfather. Initially, their relationship is very good, however, a friend of Ha Neul, out of jealousy, fabricates stories about Ae Rin speaking ill of Ha Neul’s family background. Back to the present, Ae Rin chooses to disable the Genie account. That evening, Ho In takes Ha Neul out to eat, and although Ha Neul wants them to post a dating photo, he absolutely refuses. Ha Neul returns home and discovers that her Genie account has been disabled. The next day, there is much speculation about why Genie disappeared, with hundreds of false rumors. Ae Rin feels that Genie is indeed a deception and even contemplates deleting the account. However, that day, an unusual event occurs; a new student is introduced to Ae Rin’s class, and this person looks exactly like Genie, a complete photoshop version of Ae Rin.