Kira was a normal girl until one day when she was six years old, her sister told her about the "Übermensch", which is the ultimate organic lifeform who is the new god/goddess of this world...
The Übermensch to her, is someone who lives only because of their love for the natural world and life, and someone that has no evil in them. Kira belives that YOU are the Übermensch, even if you are the most evil/timid person in the world, and she will respect you with her life...