Mari Mutou hails from Cebu, Philippines, establishing her Filipina heritage and enriching the Mutou family's multicultural identity—her daughter Ayumu embodies this blend as Filipino-Japanese. As matriarch, she is Koichiro Mutou’s wife and mother to Ayumu and Go Mutou. Her resilience surfaces early when she survives a plane crash amid the initial earthquake sequence.

Her past as an Olympic swimmer proves critical during survival scenarios, notably when she dives to untangle a rope from a submerged ship’s propeller. This act is jeopardized by an undisclosed medical condition: a solar-powered pacemaker. Volcanic ash blocks sunlight, causing the battery to fail and resulting in her death during the rescue. She chooses this sacrifice over a passive demise on the boat, reflecting her proactive nature.

A recurring trait is her documentation of moments through instant photography, capturing images of family, fellow survivors, and encountered individuals. She annotates these photos and gifts them to others, preserving memories amid catastrophe. This habit narratively foreshadows transitions or impending tragedies.

Her Filipino heritage occasionally exposes the family to prejudice during evacuations, highlighting xenophobia when rescue priorities favor ethnic Japanese citizens. Her background subtly influences family dynamics, emphasizing inclusivity and resilience as core values passed to her children. Posthumously, her photographic legacy endures in a closing montage, underscoring her role in fostering hope and continuity.