Is Juuou Mujin no Fafnir coming back?

No — Juuou Mujin no Fafnir ended on March 26, 2015, on TBS.

Juuou Mujin no Fafnir was an anime series that aired in 2015. It was a fantasy and romance story set in a world where monsters called "Dragons" appeared twenty-five years prior, leading to the birth of superhuman girls known as "D girls." The series focused on Yuu Mononobe, the only male "D" in existence, who enrolled at Midgar, an academy for D girls. The plot followed his interactions with Iris, a delinquent D girl, and his reunion with his long-lost sister Mitsuki, as they faced the threat of seven dragons that could destroy the world.

The show featured a cast including Manami Numakura as Mitsuki Mononobe, Rina Hidaka as Iris Freyja, and Yoshitsugu Matsuoka as Yuu Mononobe, among others. Since the series concluded in 2015, there are no upcoming episodes or seasons scheduled. The series remains a complete story from its original run.