"Horimiya Piece - Episode 5" begins on a cold, snowy day. The episode mainly revolves around the Iura family and focuses on the interactions between siblings Motoko and Shu Iura.

Motoko receives a call from a boy named Kitahara, who is interested in her. However, due to a misunderstanding, Shu hangs up the phone, leading to a heated argument between the siblings. Motoko is upset because she has feelings for Kitahara, but she believes Kitahara is interested in someone else who already has a boyfriend.

Later, at Katagiri High School, Shu and his friends discuss their upcoming English essay test and plan to go out to eat. Meanwhile, Motoko sends Shu a message, informing him that she has a friend visiting and that he should take his time coming home.

After school, Kitahara asks Motoko if they can study together since they are applying to the same school. Motoko agrees, and Kitahara comes over to her house. Shu, who is at home, is initially hostile toward Kitahara, but eventually, they begin to understand each other.

As the episode progresses, Motoko confides in Shu about her feelings for Kitahara and her insecurity about not being pretty enough. Shu reassures her that she is cute and that people at school often say so.

The next day, Shu, Motoko, and their friends accidentally arrive at school too early. They spend their time strolling around the school and chatting comfortably. During this time, Shu runs into Kitahara, leading to an awkward encounter.

Toward the end of the episode, Shu's friends tease him about his interactions with Kitahara and suggest that he should get a girlfriend. However, Shu insists that he likes girls and is not interested in Kitahara.

The episode ends with Shu, Motoko, and their friends enjoying their time at school despite the initial misunderstandings and confusion.