"Horimiya Piece - Episode 4" takes place in a cozy, family-oriented setting, primarily around a kotatsu, a traditional Japanese heated table. The episode begins with the Hori family and Miyamura studying for their upcoming exams. Kyosuke, Hori’s father, tries to join them but is playfully dismissed due to lack of space.

A humorous situation arises when the group—including Hori, Miyamura, Kyosuke, and Sota, Hori’s younger brother—falls asleep around the kotatsu. When they wake up, their legs are tangled in an awkward position. The situation escalates when several of them need to use the bathroom. After a series of comical exchanges and failed attempts to free themselves, they finally manage to break loose.

Later, Sengoku, the student council president, is "kidnapped" by Kyosuke and brought to the Hori household. The group spends time playing video games and sharing stories. A photo album reveals that Sengoku’s father and Hori’s parents were friends in high school, prompting them to reminisce about their past.

The episode also introduces a new character: Kakeru, Sengoku’s father. Kakeru warns Miyamura about the eccentricities of the Hori family, but Miyamura doesn’t seem bothered. Kakeru also disapproves of Sengoku having a girlfriend, leading to a funny and heated argument between him and Kyosuke.

The episode ends with a sweet moment between Hori and Miyamura. Hori feeds Miyamura mandarins, and Miyamura cleans her finger—a nod to their deepening relationship. The episode concludes with the group resuming their study session, with Miyamura deciding to focus solely on classical literature.

Throughout the episode, the characters’ actions primarily revolve around their interactions with one another, highlighting their relationships and the familial warmth of the Hori household. The episode is filled with humor, friendship, and a touch of romance, offering a comforting viewing experience for fans of the series.