Shizuku

Shizuku is the reason for the travels and journeys the girls have had. Shizuku can be recognized by light green hair and her only article of clothing is a poncho.

She is portrayed as a goddess of the dandelions. For most of the anime she is referred to by the three sisters as "The One" as they do not know her name.

~!When the sisters finally meet Shizaku, she gives them a test to allow them to go back to an era when they were happiest or continue to travel.!~

(Source: Wikipedia)