It's Not Easy Being Your Love Rival's Big Brother - Chapter 1

The world ended, seven days of earthquakes, volcanic eruption and then came the meteor storm, bringing something worse—mutation.Now, survivors are group into Shifters, mutated humans and normals.Ava Zhang was supposed to be a Normal. Useless. Disposable.Thrown into a military-controlled bunker, she is sorted into Level Three—the bottom rank, where the weak are left to rot. Starving, overworked, and surrounded by desperate scavengers, she realizes that in this world, strength decides survival.But Ava isn’t as powerless her hidden System activates. The Blueprint System—an ability that lets her design and invent anything, from weapons to high-tech defenses.

Yang Feng somehow transmigrated into a different world and received a legacy of an ‘ancient high tech’ family, which does not directly raise his power, but gives him the technology to build things which are way more advanced than the seemingly medieval world.