Unlimited Fafnir

25 years before the start of the series, massive creatures known as Dragons began appearing around the world, causing widespread destruction before vanishing. Shortly afterwards, humans with powers similar to that of Dragons were born and came to be known as D. At present day, the world's only male D, Yuu Mononobe, is transferred to Midgard and encounters a naked girl, Iris Freyja, at the beach. Iris mistakes him for an intruder and unsuccessfully tries to attack him, but then loses consciousness due to her attack backfiring and is saved by him. While the two talk, Yuu is approached by his sister, Mitsuki Mononobe, who announces to him that he will be a Midgard student henceforth.

Loki tells Yuu that it is his duty to prevent the girls at Midgar from becoming dragons and to kill them if they do. Iris has been having suicidal thoughts as she is dangerously close to becoming a dragon, but Yuu convinces her to think about living. The girls prepare for combat as Leviathan approaches the island.

While the girls are fighting Leviathan, NIFL soldiers attack Iris to stop her from becoming a dragon. Yuu protects Iris by defeating the soldiers using his dark matter guns. The girls penetrate the barrier with a coordinated attack and Yuu destroys Leviathan using the Babel cannon with Iris supplying dark matter to power up the attack.

Tear enrolls at Midgar Academy and claims Yuu as his wife as he was the person who saved her life when a fire burned down her home.

Tear's background is revealed as her family was killed when a dragon cult led by Kili burned her home and killed her parents. Tear takes pride in being a dragon because the cultists hold her in high regards, but Yuu convinces Tear to live as a human rather than a dragon. Kili arrives at Midgar to initiate an attack to take Tear away with her.

Kili attacks Midgar with the dragon Hecatoncheir that can regenerate. While Lisa looks after Tear, she is attacked and overpowered by Kili. Wanting to protect her friends, Tear agrees to go with Kili and become the Basilisk's wife. But Yuu convinces Tear not to go with her while he awakens the power of Leviathan to defeat Kili.