Uchida, a shy and introverted boy at Aoyama’s elementary school, endures relentless bullying from classmate Suzuki yet steadfastly maintains friendships with Aoyama and Hamamoto. Though reserved compared to Aoyama’s boldness, he engages earnestly in their collective quest to unravel the forest’s mysteries—the enigmatic penguin appearances and the hovering water sphere. His loyalty and inquisitive drive lead him to join scientific experiments, meticulously measuring the sphere’s traits and documenting penguin behaviors. Despite his quiet demeanor, flashes of courage emerge when confronting Suzuki or aiding Aoyama in escaping a school lockdown to address the sphere’s escalating threat.

Acting as both emotional anchor and hands-on helper, Uchida tends to the penguin Penta, joins Aoyama on exploratory train rides testing spatial anomalies, and ventures into the sphere itself to rescue trapped scientists. While Hamamoto’s intellectual assertiveness sometimes eclipses his input, he remains an unwavering ally. Pivotal moments—battling Jabberwock creatures or navigating the sphere’s destabilizing effects—spur his gradual shift from reticence to resolve. During the crisis climax, his critical support in evacuating researchers and enabling Aoyama’s final strategy underscores his evolution from cautious observer to vital collaborator in confronting the supernatural chaos.