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

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

Jo Jia goes to Mingyu's house. She makes her first mistake, but she must keep pretending she's a robot.

Mingyu decides to keep Jia. Meanwhile, Jia discovers Mingyu is the head of KM Financial.

Mingyu believes Jia is a robot and agrees to train her for a month, making Jia face many obstacles.

Jia discovers Mingyu is her brother's boss. Meanwhile, Hwang Yoocheol hears about Santa Maria and Aji 3.

The cause of Mingyu's allergy is told. Also, Jia saves Mingyu's life when he gets an allergic reaction.

Hong Baekgyeon wonders if it's okay for Jia to stay with Mingyu and realizes he still likes her.

Mingyu becomes hopeful of curing his allergy. But Baekgyeon is mad that Mingyu and Jia are getting closer.

Baekgyeon punches Mingyu, brings Jia home, and tells her she doesn't need to see Mingyu anymore.

When it is time for Jia to leave, Mingyu shows Baekgyeon his allergic reaction to keep Jia by his side.

Mingyu learns how to kiss and tries to kiss Ye Riel on a date. Baekgyeon follows them in secret.

Jia kisses Mingyu first, which makes him feel confused and makes him keep a distance from her.

When Baekgyeon sees Mingyu ordering Aji 3 to do household chores, he volunteers to do them himself.

Baekgyeon says Aji 3 will be ready in three days. Mingyu goes on a date with Riel and meets her dad.

Baekgyeon realizes why Jia broke up with him. Meanwhile, Yoocheol shows up at the start-up competition.

Baekgyeon is shocked when Mingyu says he likes Aji 3. Meanwhile, Dr. Oh tells Jia about his allergy.

Mingyu tells Baekgyeon how he always waits for Aji 3 to come, but he says Mingyu is too lonely.

Jia is sad about lying to Mingyu. But Mingyu has to reset her memory and misses her when she's gone.

Mingyu calls Jia for a delivery service, but she rejects it. Meanwhile, Jia sees Mingyu with Riel.

Mingyu sees Jia on the train and follows her. Mingyu almost finds out the truth about Jia and Aji 3.

Mingyu tries to stop Jia from going away, but Jia tells him that she isn't Aji 3 but only a model for it.

Locked up in a storage room, Mingyu tells Jia about his story. She feels sad but decides to leave him.

Mingyu ends up returning to the beach to see Jia again. Meanwhile, he realizes Aji 3 kept a backup folder.

Mingyu discovers all about what Jia has done to him. From the shock, Mingyu gets an allergic reaction.

Jia keeps coming to see Mingyu. Meanwhile, Mingyu finds out Jia created the Heart Balls.

Jia and Mingyu confess how they feel about each other. Meanwhile, Riel hears that Yoocheol will marry her.

When Martin Bold becomes impatient, Hwang Dowon promises that Aji 3 will be ready soon. Mingyu tries to protect Aji 3.

Mingyu tries to stop Dowon and bring Aji 3 back, but Aji 3 is nowhere to be found, making Martin furious.

Yoocheol learns about the cause of Mingyu's allergy and decides what to do about the board meeting.

Jia pursues her own dreams, while Mingyu and Yoocheol become good partners in leading KM Financial.