Kasuke attends the countryside school where Saburo Takada transfers, joining fellow village children in observing peculiar incidents surrounding the new student—especially during strong winds. He first proposes that Saburo might be Matasaburo, a wind spirit from local legend, when a fierce gust rattles classroom doors and eerily sways surrounding trees as Saburo subtly shifts position. This follows Saburo's abrupt disappearance and reappearance with their teacher, intensifying the children's supernatural suspicions.

Kasuke engages with classmates by comforting younger children who cry at the red-haired newcomer and mediating disputes. He later connects Saburo’s temporary vanishing amid one conflict to the children's misbehavior, strengthening the link between Saburo and the wind spirit. His dialogue reveals knowledge of folklore describing Matasaburo’s arrival on the first day of September.

During outdoor classroom formations, Kasuke stands among fifth-grade students with Saburo positioned directly before him. His visible discomfort at Saburo stretching his arms backward during lineup reflects recurring unease around the transfer student. Kasuke operates as the primary instigator of the "Matasaburo" theory among the children.