Gō Mutō is a seven-year-old boy of mixed Japanese and Filipino descent, with medium-length brown hair, thick eyebrows, and olive skin. He is the son of Koichiro Mutō and Mari Mutō, with an older sister named Ayumu Mutō. His primary passion is online video games, often played on a handheld console. He dreams of competing in the Olympics through e-sports and aspires to relocate to an IT-advanced country like Estonia.

When the initial catastrophic earthquake hits, Gō remains engrossed in his game until his lunch falls; he quickly reassures his online friends he is safe. A subsequent, more severe tremor causes debris to strike him, resulting in injuries that bleed from his eyes. Remembering his father's advice, he evacuates outside. Nanami Miura later finds him at a hillside shrine and applies bandages. His father examines the wounds, determining only his eyelids are cut, and credits Gō's gaming-honed reflexes for avoiding worse harm. Koichiro closes the cuts with a stapler, prompting Ayumu to remark it resembles a piercing.

Throughout the survival journey, Gō endures extreme conditions with his family and fellow survivors. Stranded on a rescue dinghy with Ayumu and no supplies, he jokes darkly that she should eat him if he dies, specifying a preference for being cooked "medium." His gaming background surfaces occasionally, like during an interaction with Kunio Hikita at a shop. The narrative contrasts Gō's younger perspective—symbolizing a potential future beyond Japan—with the sacrifices of older characters.

A recurring motif involves family photographs, including one Mari takes shortly after the earthquake, capturing their survival. This act of documenting moments persists amid the ongoing disaster, reflecting a theme of memory preservation. Gō survives the archipelago's sinking, ultimately enduring the events as one of the few main characters.