After Oh Laura loses her son, Nam Sin, to her father in law, Nam Gun Ho, she creates an AI robot that looks exactly like Nam Sin. Nam Sin grows up to as the heir of a rich conglomerate, PK group. He is infamous within the society for his reckless acts. However, he has no intentions of following his grandfather’s footsteps and runs away.

Nam Sin goes to Czech Republic to find his mother, Oh Laura. Oh Laura goes to the market with Namsin. At the market, both Nam Sin and Namsin, the robot, are shocked to see each other. Meanwhile, Seo Jong Gil orders a man to assault Nam Sin to get rid of him and take PK group for himself.

Young Hoon, Sin’s personal secretary, follows Sin into Czech Republic. After seeing Nam Sin in a coma and Oh Laura taking care of him, Young Hoon feels shocked. Meanwhile, Gun Ho, the CEO of PK group, tries to fill in for Sin’s presentation of their Driverless Car Project, but Mr. Seo gives the presentation instead.

So Bong barges into the presentation room and tries to argue with Nam Sin, but she fails. She tries to argue with him again at a club with Ms. Jo’s help, but that is stopped too. However, a fire breaks out at the club. So Bong ends up stuck beneath collapsed debris, but Namsin helps her out.

Namsin gets praised as a hero after saving people’s lives at the fire accident. However, as the ambulance takes him, Laura stops the ambulance and takes him elsewhere. After hearing this, Jong Gil gets suspicious and barges into the operation room where Namsin is.

So Bong asks Namsin to take her in as his personal bodyguard, and Namsin decides to take her in. However, Namsin and Young Hoon are still suspicious about her, so they keep an eye out for her. Meanwhile, So Bong follows Young Hoon to PK hospital after hearing his conversation on the phone.

So Bong is shocked to see there is another person that looks just like Nam Sin. She reports to Mr. Seo, but he only cares about taking Nam Sin, Laura, and Young Hoon out of his way. Meanwhile, So Bong gets sure about what she saw and sets up a plan with Ms. Jo to get evidence to prove that she was right.

Namsin makes So Bong think that she was mistaken. Meanwhile, the test driving of the driverless car is held in front of many reporters. However, as Sin and So Bong follow the driverless vehicle, they realize that something has gone terribly wrong.

So Bong is shocked to learn that a robot has been pretending to be Nam Sin. Young Hoon tries to persuade her to keep the secret about Namsin3 and Nam Sin. However, So Bong insists that she should meet Mr. Seo. Meanwhile, Laura tells Young Hoon not to let Namsin get near the driverless car.

So Bong has found out the true identity of Namsin3, but he treats her like a friend. The more he does that, So Bong becomes uncomfortable. In the end, she tries to leave PK group and Namsin. Meanwhile, the chairman rushes his plans to make Nam Sin and Ye Na get married to each other.

So Bong is shocked to be suddenly kissed by Namsin3. In the end, she realizes that Namsin had no bad intentions on this action and decides to continue helping him. However, Ye Na becomes jealous of this and tries to start living with Nam Sin’s house. Meanwhile, So Bong tells Mr. Seo about Ye Na to get rid of her.

Jong Gil overhears Chairman Nam throwing a fit as his dementia kicks in, so he tries to confirm what he overheard. Young Hoon asks Ye Na to find out if Jong Gil is sure about what he had heard and tells Namsin. Meanwhile, Jong Gil tries to confirm what he heard by threatening Ho Yun with her child.

Namsin tells Chairman Nam that he doesn’t have dementia. Jong Gil becomes sure that Chairman Nam has dementia and tells So Bong to stay silent about it. Meanwhile, Namsin finds out about Hee Dong’s secret and offers a deal to Ho Yun. However, Namsin gets in trouble as he becomes unable to resupply his battery on time.

Everyone is surprised as Ye Na suddenly steps up and rushes getting married with Nam Sin. So Bong’s father hears about this and visits PK Group out of anger. Meanwhile, So Bong feels uncomfortable as Ye Na keeps mistreating Namsin. This makes her step up to stop Ye Na from mistreating Namsin.

Chairman Nam finds Laura and tries to persuade her. However, Laura strongly rejects doing anything for Chairman Nam, so Chairman Nam keeps an eye on her just in case. Meanwhile, everybody is surprised to see that Namsin is showing unexpected behavior. This causes Ye Na to take a step further in rushing her wedding.

Laura and Young Hoon only care about the human, Nam Sin. However, So Bong thinks that is unfair for Namsin even if he’s just a robot. Jong Gil starts to suspect So Bong and gives her a warning and one last mission. Meanwhile, Namsin goes out to find So Bong as he can’t find her location since her phone gets turned off.

Namsin starts to think and act on his own after So Bong leaves him. Laura becomes worried that Namsin’s identity as a robot might get revealed as he starts to continue to show unexpected actions. This makes her meet So Bong herself. Meanwhile, Jong Gil’s agent follows Laura and finds out that So Bong might be deeply involved with her.

So Bong just can’t forget about Namsin after turning her back on him. She ends up visiting Laura’s hideout to meet him. Namsin is very happy to see her again, but So Bong only tells him that he should do as Laura and Young Hoon tells him to do. Meanwhile, Jong Gil sends out his agent to find out what secrets So Bong holds.

Namsin leaves the wedding ceremony on his own to save So Bong. After saving So Bong, he chases after Jong Gil’s agent. Laura become furious because Namsin keeps getting out of control. Meanwhile, Laura and Young Hoon are shocked to hear that Nam Sin isn’t showing any progress and is becoming a lost case.

Jong Gil gets more and more suspicious about the true identity of Namsin. Namsin tries to know more about So Bong after becoming friends with her. Laura is troubled as Namsin gets completely out of her control. Meanwhile, something happens at the hideout while nobody is looking.

Laura is overwhelmed with joy as she finds out that Sin is getting better. However, she gets more nervous as Namsin continues to make decisions on his own. Ms. Jo tells So Bong that she has a video of Namsin breaking down a car with his bare hands and demands answers to her questions. Meanwhile, Laura tries to hide the truth about Sin getting better from So Bong and Namsin.

So Bong is upset to see Namsin continuing to listen to Laura without knowing that he has a kill switch installed in himself. Jong Gil finds where Ye Na is and tries to get into Laura’s house. However, this causes Ye Na to panic and do whatever she can to keep Jong Gil away from Nam Sin.

So Bong confesses her love at the presentation, but unexpected events continue to occur. Nam Sin sees Laura after 20 years, but he acts coldly to her since he is angry about the very existence of Namsin3. Meanwhile, So Bong tries to negotiate with Laura to take away the kill switch from her.

After hearing So Bong’s love confession, Namsin tries harder to understand and feel emotions. However, Sin is more frustrated after meeting Namsin and starts to wonder what Laura really thinks about Namsin. Meanwhile, So Bong’s dad, Jae Shik, is shocked to realize that his daughter is in love with a robot.

Nam Sin becomes more and more angry as he gets rejected by So Bong and realizes how Laura really feels about Namsin. This makes him call Jong Gil to the hideout. Namsin and So Bong return to their daily lives. Meanwhile, Chairman Nam invites Namsin to discuss about when and how he will give him his position.

Nam Sin knows that everyone has done what they did for his own good, but he gets so angry that he says harsh things to Young Hoon. Chairman Nam offers his position to Young Hoon to see what he thinks, but Young Hoon’s reply wasn’t what he expected. Meanwhile, So Bong decides to never leave Namsin’s side.

Nam Sin feels threatened by the robot Namsin and decides to go to work even if he hasn’t fully recovered yet. So Bong continues to work as Nam Sin’s bodyguard to protect Namsin. However, Nam Sin has his own reasons to go to work. He tries to find something without telling even Young Hoon about it.

Nam Sin becomes angrier as he continues to find Namsin’s traces everywhere he goes. He tries to get rid of such traces and find a way to make Namsin get in trouble. Chairman Nam calls Namsin, and Namsin visits David after hearing shocking news. Meanwhile, Nam Sin overhears the conversation between Namsin and David.

Nam Sin becomes furious as he realizes that Chairman Nam has known that he had been replaced by a robot. His anger leads him to ask Laura if there would be any way for him to destroy Namsin. Laura tries to avoid the situation, but she ends up giving him access to the manual mode as he demands.

Jong Gil calls out Nam Sin by saying he has something to tell him. Another error occurs in Namsin’s system, and he sees a hallucination of So Bong. This makes him unbearable to hold back anymore, so he goes to see So Bong. Meanwhile, Nam Sin tries to get back at Chairman Nam after hearing a recorded message from Jong Gil.