[Multiple protagonists, BG+BL, there are four main pairs of CPs, a science girl Thinking about it this way, I feel like CP is quite loving...]
This is the 121st year since the end of the world. The battle between zombies and humans has gradually calmed down. Humanity has basically adapted to the dangerous apocalypse. However, the good times did not last long, and the stable life did not last long. A second evolution of zombies plunged mankind into a greater crisis. People call it - the "second apocalypse"!