In the year 2013, Shizuku Rossellini, a high-ranking member of the global Knockers crime syndicate "Rossellini Family," visits Gin Satsujin, a "non-Knocker" who has been ridiculed in a corner of the Knockers crime syndicate. For some reason, she has chosen him to fight as her "knight" in the "Rossellini Cup," a competition to determine the successor to the previous "King," who died a month earlier. Satsujin refuses to participate as a "non-Knocker," powerless in duels between Knockers, but then an assassin targeting Shizuku attacks. Satsujin flees in panic after witnessing the immense power of the Cavalier, but when Shizuku, who for the first time in his life acknowledged and needed him, is in danger, he instinctively leaps out. At that moment, the spear he borrowed from Shizuku speaks, something begins to cover his body, and before he knows it, Satsujin is riding the Cavalier. Thus began a battle to overthrow the organization, fought by a powerless "non-knocker" knight, a high-ranking executive ostracized by the organization, and a Knocker who himself could not use his own abilities.