Denizens of Lux have come to call it "The City" and treat it as a sentient force. Three factions vie for control of the city: the Organo, a strictly professional conglomerate with ties to the criminal underworld in the prosthetics business; the Union, a fanatical populist group interfering with Organo's affairs; and Racan, a marauding group of Texhnolyzed youths.

Rikka is a ninja descendant. Her grandfather Hyoe is the last chief of their ninja clan and her father is a cyborg researcher. Both are killed when a weapons' company raids his lab to use his research. Rikka sets out to avenge their deaths.

After making a promise to stand on the top of the Twinkle Series with her trainer as a child, horse girl Narita Top Road has been practicing diligently ever since. After winning several races, Top Road's efforts finally pay off when she earns a chance to participate in the race she has always dreamed of: the first race of the prestigious Classic Triple Crown, the Satsuki Sho. However, winning the Satsuki Sho is no simple task. Numerous brilliant horse girls are also joining the race—including two other rising racers—the flamboyant T.M. Opera O and the reserved Admire Vega, who seeks revenge against Top Road for a previous defeat. Although triumphing in the Satsuki Sho and the rest of the Triple Crown races is far from guaranteed, there is nothing that can stop Top Road on her road to the top.