Uchiki Sho is a sixth-grade student excelling academically but struggling with physical activities and sports. His timid nature and lack of athletic prowess make him a frequent target of bullying, particularly from classmate Masao Oeyama. Despite this, he consistently demonstrates bravery by defending smaller or weaker children from bullies, often enduring physical confrontations. Uchiki aspires to become an astronaut, reflecting his strong interest in space and exploration. He maintains a close friendship with Eri Kasuga, who harbors romantic feelings for him; however, he remains largely unaware of her affections, missing subtle romantic cues. This places him within a love triangle involving Eri and another classmate, Sunemi Koganeyama. When Eri is threatened or harassed—especially by Oeyama—Uchiki displays unexpected courage, intervening directly despite personal risk. This protective instinct sometimes triggers intense defensive reactions from Eri on his behalf. Academically, his abilities position him as a rival to Sunemi, though their interactions extend beyond competition. Uchiki's character development centers on his quiet resilience amid bullying, his unwavering dedication to his astronaut dream, and his role as both a catalyst for Eri's protective actions and an anchor in her personal life. His relationships and personal goals remain integral to the series' exploration of childhood dynamics.