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

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

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

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

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

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

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

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

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

Baek Gyoon punches Min Kyu, brings Ji A home, and tells her she doesn't need to see Min Kyu anymore.

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

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

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

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

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

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

Baek Gyoon is shocked when Min Kyu says he likes Aji 3. Meanwhile, Doctor Oh tells Ji A about his allergy.

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

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

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

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

Min Kyu 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 Kyu tells Ji A about his story. She feels sad but decides to leave him.

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

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

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

Ji A and Min Kyu 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 Kyu tries to protect Aji 3.

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

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

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

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