Magic Knights are modern magic-users who fight with weapons converted from their souls. Ikki Kurogane goes to a school for these Magic Knights, but he is the "Failed Knight" or "Worst One" who is failing because he has no magical skills. However, one day, he is challenged to a duel by Stella, a foreign princess and the "Number One" student. In this duel, "the loser must be obedient for life."
Ash is a student at Ansalivan Dragon Academy, attended by children who have formed contracts with dragons. He possesses the "star mark," the sign of a contract, but since his partner hasn't been born yet, he seems insignificant. The awakening of the dragon he's raising inside his body is triggered by an incident, and it emerges in the form of a young girl.
Kinjirō Sakamachi has gynophobia (fear of women), due to his violent mother and sister. Subaru Konoe is the butler of his classmate, Kanade Suzutsuki, and has to dress as a male due to butlers having to be men. When Kinjirō discovers Subaru's secret, Kanade promises to cure Kinjirō of his phobia. Kinjirō and Subaru are forced due to circumstances to spend time together and defend Subaru's secret while trying to cure Kinjirō's fear.
Enter Sentan, a lush, tranquil island encased in war between the military and those with Hiruko, known as X'amd. On one of these warlike days, Akiyuki Takehara heads off to school and gets caught in a raid by the creatures. Through a series of events he is transformed into a X'amd, and with the help of a Tessikan woman Nakiami along with his highschool friend Haru, Akiyuki is forced to learn to live with the Hiruko or faces the danger of losing his self-control and turn to stone.