Io

Io is a peculiar and shy girl with green hair who appeared in the episode, "The Traveling Swamp".

History
Prior to living in the swamp, Io was told that she was to be sacrificed by her village, becoming the bride of the river spirit, in order to prevent a flood. She managed to save her village and took up residence in the swamp, and she would eventually become engulfed by the Suiko mushi, transforming her hair to an unnatural hue of green.

Years later, Ginko was traveling through the mountains, noticing the peculiar on-and-off appearances of the swamp as he went along. When the swamp reappeared, he discovered Io standing in the water. Ginko spoke to her, and found out a little bit about her past and how the swamp saved her life. Ginko and Adashino looked at maps from Io's time period and saw that the old travelling rivers lead to the sea, as if to die. Ginko made an arrangement to save Io's life. Though the attempt seemed to have failed at first, some fishermen discovered her body awash on the shore the next morning, though she was transparent and unconscious.

Io managed to survive and began a new life in a nearby village, sad that the swamp had died on the shore, but happy at the same time. The villagers welcomed her with loving arms, as the swamp's death had provided the village with a prosperous bounty of fish to eat.

Trivia
Her name is learned only later, when Adashino addresses her, after her hair is back to normal.