DNA Lover

So-jin, a DNA researcher, gets dumped by his boyfriend, Sang-min. Heartbroken, she drinks too much and breaks into a stranger's house. Yeon-woo, a successful gynaecologist, breaks up with his girlfriend as he gets sick of her. Kang-hoon, a hardworking firefighter, finds a pregnant woman unconscious. Meanwhile, So-jin witnesses Sang-min walking down the street with a woman she knows.

Yeon-woo is still in trauma from what So-jin did to him in his house the other night. He demands that So-jin make an antidote to the hair growth solution within 24 hours. Meanwhile, while looking into the DNA of one of Yeon-woo's patients, So-jin makes an important discovery. She hurries to Yeon-woo's hospital to save a life.

So-jin discovers that Yeon-woo has a special scent that she's attracted to, so she decides to figure out if he's her DNA lover. So-jin meets her sister and mother to commemorate her dad's death anniversary at Kang-hoon's restaurant. The family gathering doesn't go too well, and they end up fighting. Yeon-woo, who happens to be at the restaurant, overhears So-jin's family's history.

So-jin finds out that Yeon-woo has the Indecent Octopus Tentacles Gene and thinks he's a cheater. She breaks the news to Yeon-woo, which leaves him flabbergasted. Meanwhile, the woman Yeon-woo's father is seeing gets the DNA test done for the baby in her womb and hears shocking news.

Yeon-woo saves So-jin from Oh Sang-min, her ex. Yeon-woo tries to kiss So-jin, and Kang-hoon witnesses it. Kang-hoon warns Yeon-woo to stay away from So-jin and not to hurt her. However, Yeon-woo decides to continue with the experiment So-jin suggested. Meanwhile, seeing how Yeon-woo keeps appearing in her path, So-jin starts to believe that the two of them share a telepathic gene.

So Jin fails to meet Yeon Woo at the Han River, and she runs into Kang Hoon instead. Just when she thought she failed the experiment, she realizes that her telepathic message could've been interfered. So Jin and Yeon Woo go on a trip to Gapyeong to see a celestial show. Kang Hoon joins them in secret to stop Yeon Woo from hitting on So Jin.

So-jin comes to believe that the kind of food she and Yeon-woo consume will play a big part in their relationship, so she works hard to make Yeon-woo eat similar food. After learning her intention, Yeon-woo invites her to his place to cook a meal for her, but things don't go as expected. Meanwhile, Kang-hoon tries to find the cause of the fire that killed Ha Ga-hee, Yeon-woo's father's mistress.

It turns out So-jin has the BRCA gene, which makes her more likely to get cervical cancer. She ends up getting enteritis from the food she had at Yeon-woo's, and Yeon-woo decides to operate on So-jin himself. So-jin contacts her mom and sister to ask them to come on the day of her operation, but both of them refuse, leaving So-jin with no option but to be without a guardian.

Even after So-jin starts dating Yeon-woo officially, she can't let her guard down because of Yeon-woo's Indecent Octopus Tentacle Gene. Mi-eun visits So-jin's office for a consultation and ends up giving her a tip on dating Yeon-woo. So-jin decides to start a project to improve Yeon-woo's genes. Meanwhile, Yeon-woo's parents decide to get divorced.

So-jin tells Yeon-woo she loves her, but Yeon-woo has a hard time saying it back. So-jin has a harder time sharing her innermost feelings the more she sees him. Seeing So-jin being anxious about her relationship, Mi-eun suggests doing a destiny test with Yeon-woo. Meanwhile, Kang-hoon learns from Mi-eun that the basketball uniform So-jin got tested wasn't Yeon-woo's.

So-jin finds out the uniform she tested the DNA on was Hoon's, not Yeon-woo's. Yeon-woo's father passes away, leaving So-jin in shock. Without knowing where Yeon-woo could be, So-jin looks for Yeon-woo who went missing. Meanwhile, Yeon-woo shares how he truly thinks of true love and what he's afraid of the most.

Yeon-woo asks So-jin to break up with him, saying Kang-hoon is meant for her. Upon hearing So-jin's breakup with Yeon-woo, Yeon-woo tries his best to console her. Kang-hoon asks So-jin out for a date, but So-jin keeps getting reminded of the days she spent with Yeon-woo. Meanwhile, Kan-hoon falls into a critical state after a fire breaks out in an empty house.

After getting advice from A-ri, Kang-hoon decides to make So-jin's heart race for him so she can see him as a man. Yeon-woo visits Tree Orphanage which his dad sponsored for 20 years and meets Father Andrea there. Meanwhile, So-jin ends up going to volunteer work with the entire Sim Hospital staff and meets Yeon-woo for the first time after their breakup.

Kang Hoon discovers that someone was trying to set So Jin's place on fire through a flowerpot. Yeon Woo decides to quit his job at the hospital and leave for the US. He does so to prove that giving up is also proof of his love for So Jin. Meanwhile, Kang Hoon visits the plantation that provides grass trees and finds out who's been sending the flowerpots.

Yeon Woo comes to rescue So Jin who was held captive by Father Andrea's twin brother. Kang Hoon also comes to the scene, but Yeon Woo and So Jin end up getting badly injured before that. Even after the whole incident, Yeon Woo still decides to leave for the US. Upon hearing the news, So Jin goes to the airport to stop him.

After Yeon Woo leaves for the US, So Jin decides to wait for him. So Jin starts a new project where she studies the Parkinson's disease gene with the elderly in the countryside. There, she runs into Yeon Woo. They share how they really feel about each other and the things they learned during the year they were apart.