The revolving point of the whole story is the child-like being that Shu encountered in the first episode; she has special water powers which can be invoked with her pendant, but she no longer wants these powers to be used by humans in general (she specifically does not want them to be used by Hamdo for his deeds). Apart from the fact that each use of these powers permanently weakens her physical state, she has also found that the initial gratitude people show for the use of these powers later turns violent when she refuses to use them. She rarely talks, nor does she show any emotion.

(Source: Wikipedia)