Rain Is Her Old Acquaintance

The sky was so gloomy that it was dripping with water. Crowds of people disappeared like streams of data, streets cracked and apocalypse descended. Song Zhiyan stood at a high place, her mood as calm as dead water. She thought she might be crazy. Until the heavy rain fell, Bingsi took action—— The system note lights up: Yu is her old acquaintance. But who is Yu's old friend?