Gou Mutou is the seven-year-old younger brother of Ayumu Mutou and son of Mari and Kouichirou Mutou. Living in Tokyo with his family before catastrophic earthquakes devastate Japan, Gou is a dedicated video game enthusiast who frequently declares his ambition to become a professional esports player. His dialogue habitually incorporates random English words and phrases, drawing occasional corrections from others.

Forced to flee Tokyo after the initial quake, Gou journeys across the collapsing archipelago with his family. He witnesses the deaths of multiple family members and companions, including his father Kouichirou early in their escape. These profound losses compel him to confront extreme hardship and mortality. Amidst constant danger and psychological strain, Gou gradually hones practical survival skills alongside his sister.

Surviving the entire ordeal, Gou reaches safety as one of only two remaining Mutou family members, alongside Ayumu. The experiences of devastating loss, necessary adaptation, and hard-won resilience define him across the disaster narrative.