In 1983, off-duty policeman Reiden picks up a suspicious couple, Kei and Ai, who claim to be father and daughter but appear to be close in age.

Kei draws out his latent ability to the maximum by a Legendary "Trigger" and Ai blows away K2.

Their enemy is the secret society "Fraud" of para-psionics, which is commanded by Kuu Ragua Lee.

The world is now populated by Headmeters, people who have psychic powers and whose strength is shown on their forehead when they fight.

The one who is after her has a deep secret and is aided by a small dwarflike man who lives in a robotic suit.