Isamu Yamashita serves as a supporting character and classmate, closely associated with the central figure Sally. He steadily supports Sally, frequently appearing alongside him during school and club activities. Yamashita is romantically involved with Tonko, who actively encourages and assists the protagonist Chitchi in her romantic pursuits. This relationship integrates Yamashita into Chitchi's social circle. He actively joins school events and group interactions, which contribute to the situational challenges faced by the protagonist. His presence occurs primarily within educational environments and casual settings throughout the story.