An ordinary office drone named Lin Dongmou finds a glowing cube that has appeared out of nowhere in his rented apartment. He is forcibly bound to it as some kind of “Trial System Guardian.” His job is to help unlucky alien creatures stranded on Earth after failing various trials across the universe earn enough energy to return to their home planets. From a slime that can never be fed enough to a crystal scorpion that argues with people using vibration frequencies, Lin Dongmou must carefully keep these visitors from beyond the stars hidden, while also dealing with his landlady’s relentless calls for rent and the Huabei debt he can never seem to pay off. He thought this was just a troublesome side job, but gradually realizes that these “lost items” may be connected to a vast secret beyond anything he could imagine.
