Ai Shitî plot
Sometime in the future, Kei and Ai flee for their lives. Ai is a little girl with a terrible secret that could destroy the world. The world is now populated by 'Headmeters', people with psychic powers whose degree of power appears on their foreheads when they fight. Kei was an experimental subject in a testing lab and his powers don't exceed five, which is relatively much lower than others around him. But when Ai needs to be protected, his powers reach to infinity. Despite this, Ai is captured and it's up to Kei and a group of companions to rescue Ai and keep her secret safe.