Hae Sung and Jung Won are ordinary high school seniors who are getting themselves ready for life after graduation. One day, Hae Sung wakes up to find everything surrounding him different. He was dead for 12 years.

Hae Sung looks for ways to figure out what happened to him when he accidentally runs into his high school friend, Ho Bang. Ho Bang visits Hae Sung's tomb every year with the rest of Hae Sung's high school friends. It turns out that Hae Sung was killed on his birthday.

Jung Won is confused and pressured by Min Joon's confession. Hae Sung finds out how his family and friends have been living through Ho Bang, who also tells him that he and the rest of their friends lost touch with Jung Won.

Jung Won takes care of Hae Sung who was injured and lost consciousness. Jung Won thinks she's insane for thinking that Hae Sung has comeback from death. Hae Sung finds out how Jung Won's life has been difficult without him and is heart-broken.

Jung Won decides to let Hae Sung stay at her place. They spend a good time chatting about their past. The next day, Hae Sung finds a way to help both Jung Won and Hae Chul out of the gang's hands. Meanwhile, Hae Sung runs into Young Jun, but Young Jun asks her to keep his family status a secret.

Jung Won tells Min Joon that Hae Sung is her cousin, which doesn't make Hae Sung happy. On their way back home, Hae Sung and Jung Won decide to have a drink together for the first time. Hae Sung honestly tells Jung Won about how he feels about the current situation he is in.

Hae Sung finds out from Jung Won that Young Jun wasn't with her on the day Hae Sung died. The police report was recorded falsely and Hae Sung thinks it's strange. Meanwhile, Tae Hoon, who is the vice president of a department store, tells Hae Sung that Young In works in the department store. Hae Sung meets Young In, only to find out that she's been living a hard life.

Min Joon gets his wrist injured and Jung Won offers to help him. Hae Sung goes over to Min Joon's place and offers to help instead of Jung Won. Meanwhile, Gong Joo disappears from her kindergarten and Hae Chan looks all over the city to find her.

Hae Sung finally meets his youngest sibling, Soo ji. He has met all of them and had a chance to talk to each other except for Young Jun. When Hae Sung visits Young Jun at his hospital to talk, Young Jun tells him to stop acting like his real brother.

Min Joon helps and trains Jung Won into becoming the main chef of his restaurant. However, Jung Won fails the promotion test and does not make it. Disappointed Jung Won meets up with Hae Sung in front of the restaurant and hugs him, only to be discovered by Min Joon.

Ho Bang tells Hae Sung that the driver who hit Hae Sung with his car was also dead. When Ho Bang visited the driver's funeral home, the driver's wife was saying that he wasn't the real killer, which made Ho Bang suspicious. Ho Bang gets transferred to Seoul and the friends gather to send him off.

Hae Sung finds out that Hae Chul got into a fight in the restaurant because someone accused Hae Sung of being a murderer. Mr. Ahn tells Hae Sung that he gets pain in his chest whenever he's near someone who's related to his death. Min Joon gets hit by a car while trying to help Jung Won.

Jung Won gets held up at a hospital because of Min Joon's accident. Fortunately, she makes it to the fireworks festival and meets up with Hae Sung there. Hae Sung feels another pain in the chest and looks for people who might be related to his death.

Hae Sung and Jung Won have a drink at her place when all of their friends show up and catch them. Meanwhile, Hae Sung tries to convince his sisters, Young In and Soo Ji, to straighten things with their brother Hae Chul, and they all have a meal together.

Hae Sung gets saddened by the fact that he has to return when his time comes. However, he decides to make the most of his time and looks for the person who murdered him. Ho Bang helps Hae Sung by questioning Tae Hoon's father whose driver was accused as the murderer. Meanwhile, Min Joon asks his kitchen staff to come up with a new menu for the restaurant.

Hae Sung applies for a position at Min Joon's restaurant and he has to come up with a new menu to pass the test. Meanwhile, Seo Won visits Min Joon's restaurant with her colleague who used to go to the high school that Jung Won went to. Min Joon learns that Jung Won suffered a lot because her boyfriend died in high school.

Jung Won acts awkward in front of Hae Sung because she was reminded of the time she suffered because of his death. She feels guilty as she thinks it's all her fault that things turned out the way they are. Meanwhile, Min Joon confesses to Hae Sung that he likes Jung Won.

Hae Sung and Jung Won find out how they feel about each other and kiss for the first time. They go on a trip together and make memories that they couldn't have over the past years. Meanwhile, Hae Sung caters for Chung Ho Foundation and feels immense pain in the chest.

Hae Sung faces the culprit who's been causing a pain in his chest. It turns out to be Tae Hoon's father, Gwon Pyo. Gwon Pyo feels pressured as Hae Sung and Ho Bang are narrowing down on him. Meanwhile, Soo Ji's condition doesn't get better and she still hesitates to tell Young In about it.

Gong Ju's mother visits Hae Chul, but Hae Chul tells her to leave them alone. Min Joon's uncle turns out to be the driver who is known as the culprit, and Min Joon has the evidence to prove that his uncle did not kill Hae Sung.

Hae Sung is in big shock after hearing who the real culprit behind the murder was. Min Joon tries to bring the truth into light with his aunt’s testimony, but he’s put in more danger by Gwon Pyo’s scheme.

Hae Sung passes out in the middle of nowhere so no one can find him. Hae Sung is out of touch for a while and Jung Won gets really worried about him. He tries to make up for the time he was away from Jung Won.

Hae Sung and Min Joon start of their new business, the “Cha Pasta Food Truck”. Their food truck becomes a hot issue on social network media by a chance. Meanwhile, Jung Won submits her work to a character contest and waits for the results.

Hae Sung tries to cover up the truth behind the incident which took place twelve years ago. He tries with all his might for Young Jun. However, Ho Bang receives a call reporting the murder.

Hae Sung finds out Min Joon is the son of Chairman Cha Gwon Pyo and that he's half brother of Tae Hoon. Meanwhile, an anonymous calls Ho Bang to report on what he saw on the day of Hae Sung's death.

Min Joon realizes that his dad killed Hae Sung twelve years ago and he feels apologetic towards Jung Won. Tae Hoon wants to tell Hae Sung how he feels about Young In and get his approval. Jung Won starts working at an art gallery where she runs into a teacher who used to work at her high school.

Moon Sik turns out to be from an affluent family and all his friends feel somewhat betrayed. Ho Bang finds out there's a link between Tae Hoon's mother and the art teacher, Ms. Hyun. Min Joon finds Hae Sung in Jung Won's high school yearbook.

Hae Sung tells Min Joon the truth about his identity and asks for his forgiveness. Ho Bang keeps tracking down Hyun Kyung Eun to find out about Hae Sung's death. Meanwhile, the new restaurant opens and every staff from the previous restaurant comes to help.

Tae Hoon's father, Gwon Pyo, finds out that Tae Hoon is dating Young In and gets furious. Gwon Pyo tells Tae Hoon to stop seeing Young In. Ho Bang traces Park Dong Seok and finds out he's in Canada. Meanwhile, Hae Sung and Jung Won go on a business trip together to a remote city.

Hae Sung sees himself disappear in front of a mirror and gets scared that his day is coming. He shares that story to Ms. Do and she tells him to get prepared for the day he leaves this world. Meanwhile, Gwon Pyo tries to tell something about Young Jun to In Sun, but gets interfered.

Hae Sung realizes that Tae Hoon could be the culprit behind the murder after talking with Young Jun. Tae Hoon's mother goes and sees Young In to tell her that she doesn't deserve Tae Hoon. Young In considers breaking up with him.

Young In tells Tae Hoon that she wants to stop seeing him. Hae Sung hears what happened between them and gets heartbroken that the two of them can't overcome the difference. Tae Hoon confesses to Hae Sung what happened on the night of his death.

Jung Won tells Hae Sung that she never celebrated her birthday ever since Hae Sung died. Hae Sung felt bad after hearing this, so he wants to make her wishes come true. Tae Bok leaves Hae Sung some money in order to appreciate Hae Sung for helping him out. Meanwhile, Ho Bang confesses his feelings to Jin Joo and she ends up accepting his feelings.

Hae Sung picks the location where he will open his new restaurant with his brother, Hae Chul. Tae Hoon tells Hae Sung what exactly happened on the night Hae Sung was killed. After hearing the story, Hae Sung realizes that Tae Hoon might not be the real culprit.

Jung Won accidentally watches the video that Hae Sung's been recording and finds out that Hae Sung has to return soon. She seeks for a word of advice from Ms. Do who has a similar experience. Ms. Do gives Jung Won a couple of days off for her to spend them fully with Hae Sung. Meanwhile, Ho Bang, Jung Won, and Hae Sung realize that Dong Seok's been keeping an eye on Jung Won's every move.

Dong Seok feels threatened as he realizes that Ho Bang is looking for him and wants to run away to the States with Yoo Min. Yoo Min refuses to go without Gong Joo. Hae Chul manages to attain a cup that has Dong Seok's DNA and Ho Bang runs a DNA test to find out if Dong Seok is the real culprit. Meanwhile, Tae Hoon finds out that Soo Ji has been sick and that she's in critical condition.

Jung Won accepts the fact that Hae Sung might have to return one day and decides to make the best out of the days left. Hae Sung finds out that Soo Ji is in need of a transplant, so he gets tested to see if he's a match. Meanwhile, Ho Bang finds out where Park Dong Seok is and chases after him.

Sung Jun pulls off his wedding because he can't stand lying to Seo Won anymore. He decides to donate his kidney to Soo Ji and he makes up with his siblings again. Meanwhile, Hae Sung opens his restaurant with Hae Chul and everyone visits to congratulate them.

Dong Seok takes Gong Joo to a bus terminal and sends her off to Busan by herself. When Yoo Min and Hae Chul find this out, they chase the bus Gong Joo got on and saves her. Meanwhile, Ho Bang and Hae Sung catch Dong Seok at the airport, but he manages to run away.