Kim Min Gyu gets an allergic reaction when in contact with humans, but he says he isn't lonely.

Min Gyu orders Aji 3 for trial. But that night, the research team accidentally spills beer on it.

Ji A goes to Min Gyu's house. She makes her first mistake, but she must keep pretending she's a robot.

Min Gyu decides to keep Ji A. Meanwhile, Ji A discovers Min Gyu is the head of KM Financial.

Min Gyu believes Ji A is a robot and agrees to train her for a month, making Ji A face many obstacles.

Ji A discovers Min Gyu is her brother's boss. Meanwhile, Yoo Cheol hears about Santa Maria and Aji 3.

The cause of Min Gyu's allergy is told. Also, Ji A saves Min Gyu's life when he gets an allergic reaction.

Baek Gyeon wonders if it's okay for Ji A to stay with Min Gyu and realizes he still likes her.

Min Gyu becomes hopeful of curing his allergy. But Baek Gyeon is mad that Min Gyu and Ji A are getting closer.

When it is time for Ji A to leave, Min Gyu shows Baek Gyeon his allergic reaction to keep Ji A by his side.

Min Gyu learns how to kiss and tries to kiss Ri El on a date. Baek Gyeon follows them in secret.

Ji A kisses Min Gyu first, which makes him feel confused and makes him keep a distance from her.

When Baek Gyeon sees Min Gyu ordering Aji 3 to do household chores, he volunteers to do them himself.

Baek Gyeon says Aji 3 will be ready in three days. Min Gyu goes on a date with Ri El and meets her dad.

Baek Gyeon realizes why Ji A broke up with him. Meanwhile, Yoo Cheol shows up at the start-up competition.

Baek Gyeon is shocked when Min Gyu says he likes Aji 3. Meanwhile, Dr. Oh tells Ji A about his allergy.

Min Gyu tells Baek Gyeon how he always waits for Aji 3 to come, but he says Min Gyu is too lonely.

Ji A is sad about lying to Min Gyu. But Min Gyu has to reset her memory and misses her when she's gone.

Min Gyu calls Ji A for a delivery service, but she rejects it. Meanwhile, Ji A sees Min Gyu with Ri El.

Min Gyu sees Ji A on the train and follows her. Min Gyu almost finds out the truth about Ji A and Aji 3.

Min Gyu tries to stop Ji A from going away, but Ji A tells him that she isn't Aji 3 but only a model for it.

Locked up in a storage room, Min Gyu tells Ji A about his story. She feels sad but decides to leave him.

Min Gyu ends up returning to the beach to see Ji A again. Meanwhile, he realizes Aji 3 kept a backup folder.

Min Gyu discovers all about what Ji A has done to him. From the shock, Min Gyu gets an allergic reaction.

Ji A keeps coming to see Min Gyu. Meanwhile, Min Gyu finds out Ji A created the Heart Balls.

Ji A and Min Gyu confess how they feel about each other. Meanwhile, Ri El hears that Yoo Cheol will marry her.

When Martin becomes impatient, Do Won promises that Aji 3 will be ready soon. Min Gyu tries to protect Aji 3.

Min Gyu tries to stop Do Won and bring Aji 3 back, but Aji 3 is nowhere to be found, making Martin furious.

Baek Gyeon decides to change Aji 3's face. He deletes every video except for the emotion patterns.

Yoo Cheol learns about the cause of Min Gyu's allergy and decides what to do about the board meeting.

Ji A pursues her own dreams, while Min Gyu and Yoo Cheol become good partners in leading KM Financial.