Juuou Mujin no Fafnir

After destructive dragons appear, girls known as Ds begin to be born with similar powers. Yuu Mononobe, the only known boy with those abilities, is sent to the isolated Midgard academy, where he meets Iris and reunites with his sister Mitsuki.

School life offers little shelter when a dragon approaches the island and a changing mark places a student in danger. Protecting his companions forces Yuu to confront the secrets of his own strength and memories tied to battles he cannot fully recall.