Traveling Through Time to Save the Heroine and Saving the Earth at the Same Time

A tide of beasts lands, and humanity is destroyed. The love of his life died fighting to protect China. Bu Feiyu activates the universal upgrade system and travels back to three years before the arrival of the beast tide. I just want to be with my loved one... But I didn't expect to enter the research institute by the way, become a front-line R&D staff, become an ace in scientific research, become an ace in martial arts... By the way, the third generation of Awakening Stones was developed, and the 20% chance of the second generation of Awakening Stones was directly increased to 70%. All of a sudden, the world was shaken! But Bu Feiyu strongly demanded: "Keep a low profile, I just want to attend a martial arts class. Everyone was confused: Are you crazy! If the ground general doesn't do it well, if the chief engineer of the research institute doesn't do it, he has to go to the front line to risk his life? This novel and its characters are purely fictitious. Any similarity is purely coincidental and should not be imitated.