Somebody episode 8 starts with Kim Sum visiting Young Gi-Eun at her home. Young Gi-Eun knows Kim Sum well and tells her that she realized that the man in the picture Mok-won sent is not her boyfriend.
Kim Sum and Young Gi-Eun talk about the man who hurt her and Young Gi-Eun says she is still determined to find him. She asks Kim Sum not to interfere with her plans to catch him.
Meanwhile, on the app, Yun-o matches with a new lady and they start texting. She says that they have met before and had drinks. The account video calls him and he accepts the call. The call is strange and he keeps getting more calls from strange women who keep mocking him. They also keep saying similar things said by some of the women he killed.
Elsewhere, Mokwon receives a call from the man she had hired to look out for Yun-o at the restaurant. He asks her the reason she hired him to find Yun-o and tells her that he saw Yun-o kill the restaurant owner. He asks Mok-won to never contact him again.
After the call, Yun-o visits Mok-won and he asks her why she is interested in finding him. He tells her that he should have killed Young Gi-Eun. He says that Kim Sum excites him as she is different from Young Gi-Eun. He tells Mok-won that Kim Sum is perfect to him as she is different to most people who make him sick. He asks Mok-won not to get on his bad side and destroyed her temple’s god before leaving.
Mok-won visits Young Gi-Eun and takes all the phones she got from her investigations on Yun-o. She tells her that they are running out of time and they should contact Kim Sum. They take the phones to Kim Sum and discuss the way forward.
Mok-won tells them that he visited her house and knows that they are friends. She is sure he knows how to find Young Gi-Eun too. She asks Kim Sum to help them by sharing the information she has on Yun-o. Kim Sum refused to give them information on Yun-o and even tells them she gave him a knife. Mok-won and Young Gi-Eun are disappointed in her and they leave her house.
Later that night, Young Gi-Eun gets a visit from a mysterious person who leaves the same brand of lollipop that Yun-o once gave her.
The next morning, Yun-o kills the man Mok-won hired to be a lookout and runs over his body. He takes his phone and deactivates his Somebody profile before opening a new one using the man’s phone.
He later calls Kim Sum and shows her the plans he has for both of them. He apparently bought a house where they can hide out and wants to know the kind of space she likes. Jung and an administrator are also listening in on the call. It seems like they are working together to trap Yun-o. The administrator later asks Kim Sum if she like Yun-o and she admits that she likes him a lot.
Young Gi-Eun decides to use the help of the hacker again to trace the location of Yun-o using the dating app. She heads to the office and briefs her fellow police officers working on the case and lays out the evidence she has collected.
The police get a warrant and raid Yun-o’s office. They find many phones in his office drawers and are curious why he has so many phones.
On the other hand, Yun-o keeps getting strange calls from women he encountered on the app. This is Jung’s idea to use the messages and images of the women he has killed to drive him into a corner. He gets annoyed and throws away the phones he had on him. He goes to Kim Sum’s house and video calls her from outside.
He tells her that he kills people through the app she made. He tells he that he wishes that he had met her earlier. Kim Sum tells him that it is not too late to start over and lets him in her house. They hang out for a while and as he leaves, Kim Sum asks if they can go to their hideout and spend some time together.
Kim Sum spends the next few days trying to scientifically figure out her feelings for Yun-o. She calls Young Gi-Eun and tells her she is planning to meet Yun-o but refuses to tell her the location of their meeting. She tells Young Gi-Eun that Yun-o means so much to her and that he is special. She says she is not worried about Yun-o hurting her.
Before leaving to meet with Yun-o, Kim Sum drops by Mok-won’s house and picks up the blade Yun-o gave her. She also asks Mok-won to check Yun-o’s fortune and leaves a letter behind.
Young Gi-Eun calls the tracker to trace Kim Sum and Yun-o but something is off as Kim Sum knows they will trace her phone. She intentionally leaves it in a taxi and Young Gi-Eun and the cops end up on a tedious rabbit chase.
Yun-o receives a message from an account that is under the name Isle. It is supposed to be Kim Sum’s profile. He tells Sum on the video call that he will be waiting for her in their hideout even if she is late. He tells her that he loves her but as they continue to talk a person in a hood walks into the house. The person proceeds to slice his nose bridge and slice his throat.
It turns out that Kim Sum is the person who killed him. She then has Mok-won pick her up and goes back to work. She continues living her life as if nothing happened but she seems sad.
Yun-o had no idea the person he trusted ended up being his downfall. In a way, the series ends in poetic justice with a twist we didn’t see coming. The main message here seems to be that if you live by the sword, you die by the sword!