One day, Ningning and Feifei were playing on the slide at the park. A sudden, strange wind swept away the smiles from the once-happy children. The atmosphere in the park turned cold and eerie. At the same time, many children mysteriously vanished, including Feifei. Meanwhile, Ningning was nearly attacked by a dark shadow but was saved by someone named Xiao Yun, who claimed to be a Guardian. From Xiao Yun, Ningning learned that Feifei had been captured by a monster that feeds on happiness and taken to another dimension, where time flows differently—even if one stays there for a long time, returning feels as if no time has passed at all. Determined to rescue Feifei, Ningning embarks on a strange journey with Xiao Yun to find her.