In an underground city sealed by a crystal dome, stick figures exist like the walking dead, trapped in an endless loop. The sky has become an unreachay, perceived as an untouchable and dangerous realm. Stickman Xiao Ou's father was once chosen as a "Flyer" to venture into the unknown heights, but now left behind only a mysterious key to a flying machine. Xiao Ou gradually discovers that the "Flyers" are not heroes, and the truth about the sky is far more terrifying thagined. When fate pushes him