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.

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

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.