Koichi, also referred to as Ichiro in some versions of the story, is a sixth-grade student at a small rural school in a mountain village. As the oldest child in the class, he naturally assumes a leadership role among his peers, who look up to him for guidance and stability. He is calm, observant, and thoughtful, often taking a moment to assess situations before acting. Unlike some of the more excitable children, Koichi does not immediately embrace the idea that the transfer student Saburo Takada is the legendary wind spirit Matasaburo; instead, he watches the newcomer with measured curiosity and a sense of responsibility.

Koichi’s primary role is that of a grounded anchor for the group. When the other children are frightened or confused by Saburo’s unusual appearance and behavior, Koichi remains composed and tries to maintain order. He is protective of the younger students, intervening in fights and offering reassurance. His motivations stem from a desire to keep the group together and to understand the mysterious boy without letting fear or superstition take over. Throughout the story, Koichi participates in nearly every adventure with Saburo and the other children, including trips to the highland pasture, grapevine gathering, and swimming in the river. He is often the one who asks questions or expresses the mixed feelings the children share about Saburo.

Koichi’s key relationships include his friendship with the energetic Kasuke, who is quick to declare Saburo a wind spirit, and his bond with Saburo himself. Koichi treats Saburo with a blend of caution and openness, sometimes speaking directly when others are too intimidated. He also has an older brother who appears during the mountain excursion, further grounding Koichi in the everyday world of family and work. Over the course of the narrative, Koichi’s perspective shifts subtly. He moves from skepticism to a quiet acknowledgment that Saburo might indeed be something beyond an ordinary boy, especially after witnessing Saburo’s sudden departure during a storm. In the end, Koichi is left with the same uncertainty as the others, but his leadership and steady nature remain unchanged.

Koichi has no supernatural powers; his notable abilities are his perceptiveness, his ability to mediate conflicts, and his willingness to act as a caretaker for the younger children. He is a figure of reliability in a story filled with whimsy and unexplained phenomena, embodying the human desire to make sense of the extraordinary while still protecting the ordinary bonds of childhood.