Tsuyoshi Saigō, universally nicknamed "Godzilla," recurs across multiple adaptations. His moniker stems from his role as the primary bully in Shōta Ōhara's elementary school class and neighborhood, mirroring the destructive reputation of Toho's famous monster. Standing 150 cm tall (approximately 4'11") with black eyes, Godzilla blends aggressive tendencies with vulnerabilities—exhibiting poor academic performance and harboring a significant fear of heights.

His family operates a liquor store, and he has at least one brother. Kizao Kiza frequently acts as his lackey, assisting in bullying activities. Despite antagonizing Shōta, Godzilla occasionally displays underlying care or protective instincts toward him, indicating a complex relationship beyond simple antagonism. He maintains contact with other core characters: Q-Taro, P-ko, O-jiro, Doronpa, U-ko, Hakase, and Yoshiko Koizumi.