"Iruka to Shonen" centers on the relationship between a young boy and a mysterious dolphin-like creature named Iruka. Set in a coastal town, the narrative explores themes of friendship, loss, and the connection between humans and nature. The boy, whose name is never explicitly stated, lives a solitary life, often wandering the shoreline. One day, he encounters Iruka, a creature with the ability to communicate telepathically, who becomes his companion and guide.

The story unfolds as the boy and Iruka embark on a series of adventures, uncovering the secrets of the ocean and the town’s history. Iruka reveals fragments of its past, hinting at a deeper connection to the boy’s own life. As their bond strengthens, the boy begins to confront his feelings of loneliness and grief, particularly regarding the absence of his parents, who disappeared under mysterious circumstances.

Throughout the series, the boy and Iruka encounter various challenges, including environmental threats to the ocean and conflicts with townspeople who view Iruka as a threat. The narrative delves into the boy’s growing understanding of responsibility and the importance of protecting the natural world. The relationship between the two characters serves as the emotional core of the story, with Iruka acting as both a mentor and a source of comfort.

The plot is driven by a mix of episodic adventures and an overarching mystery surrounding Iruka’s origins and the boy’s family. As the boy uncovers more about Iruka’s past, he begins to piece together the truth about his own life, leading to a climactic revelation that ties their fates together. The series concludes with a poignant resolution, emphasizing the enduring bond between the boy and Iruka and the transformative power of their friendship.