Awakening from a mysterious cocoon, Rakka finds herself in a strange world as a Haibane, alongside others with gray wings and radiant halos. Living in the Old Home on the outskirts of the town Grie, where non-winged and halo-less individuals reside, they abide by strict rules that forbid them from approaching the towering walls. Only the enigmatic Toga have that privilege. Amid the tranquility of her daily life, Rakka grapples with unanswered questions and forbidden truths. Determined to uncover her purpose and strive towards the elusive Day of Flight, a significant event for all Haibane, Rakka must navigate the ominous consequences of failure, risking the damning label of Sin-bound.