Ryuu Tsukai wa Mada Sora wo Shiranai

Sana, a Black Dragon rider, was about to cross the Skywall with her companions to attack the White Dragon. However, they were caught in a horrific baptism by fire, and she lost her companions right before her eyes. Sana was the only one to survive, and the traumatic experience left her unable to fly. Until she meets someone.. (Source: Natalie.mu, machine translated).