Mio's mother, appearing solely in his flashbacks, died before the main story began. She possessed a youthful appearance with black hair, typically braided into a long plait, and brown eyes.

Raising Mio alone after her husband perished at sea when his boat capsized near shore, she faced financial hardship yet strived to fulfill her son's wishes. She shared activities like crafting bracelets with him, a tradition he continues by wearing them on his wrist. She also cooked his favorite meals, particularly curry and crab, creating cherished culinary memories for Mio.

Their bond was deeply woven into daily rituals, such as visiting Shun's aunt's bakery for bread. She regularly took him to the seaside at night, a place connected to his father's memory.

She died of unknown causes during Mio's adolescence; he discovered her motionless on the floor. This event triggered his social withdrawal until meeting Shun. Though physically absent, her influence endures through Mio's objects and habits, reflecting their lasting connection.