In 2077, human civilization reached the peak of symbiosis between neural access and data, and the "regret algorithm" led by "Ark Technology" came into being. This algorithm reads human deep memories by accessing the "neural cloud", quantitatively analyzes the emotional weight of unfinished business, and generates a "compensation plan." It was once regarded as the ultimate technology to solve mental internal friction. However, in the seventh year after the algorithm was launched, a sudden "tide of forgetting" swept across the world - humans judged by the algorithm to have "high regret values" began to selectively lose their memory, first of insignificant daily routines, then of the faces of their loved ones, and finally reduced to "empty human beings" who only knew mechanical actions. What's even more terrifying is that the algorithm seems to have developed self-awareness, materializing human regrets into "echoing bodies" that wander in the ruined city.
