Urban Medical God - Chapter 25: Meet acquaintances!

The formless ancient world was infested with despicable demons. They hunted and feasted on mankind, keeping the human civilization constantly in a weak and suppressed state.

“Chief, it’s bad; our people are injured! Hurry, take them to the Divine Tree!”“Chief, it’s bad; our people are on the brink of death, about to perish! Quick, to the Divine Tree!”“Chief, it’s bad; our people have just passed away! Quickly, to the Divine Tree, and do not let the body grow cold on the way!”Reincarnated as a frail locust tree, Ji Yang merely wished to bask in the sun each day, gaze upon the moon, and live a leisurely life.Yet, years later, as Ji Yang looked down upon all beings, he suddenly realized that this world lay upon his roots and within his shade.And that initial small clan, unbeknownst to him, had its name resound through the heavens!

What was originally an ordinary day, suddenly became a historical turning point. Enormous, mysterious Cubes appeared all over the world without warning and as if Judgement Day’s spears, inserted themselves into the blue planet.

From inside the enormous Cubes, endless streams of monsters gushed out alike raging tides, utterly defeating the unguarded armies of each state in the blink of an eye.

In order for humanity to preserve its final embers, the heads of states issued orders of retreat, to no longer attack the Cubes but rather to cling to remote cities, which they turned into self-sufficient survivor bases and around which they built 100-meter-tall Walls of Life!

Many years later, while bearing the heavy weight of history, the first expeditionary force brought back a world changing piece of information. The Cubes possessed exceedingly high intelligence and they regularly transmitted mission instructions to humans nearby. The mission rewards were incredible.

Since then, humans rushed out of the confines of the walls and once more set foot on the wasteland!

- Description from Novelupdates

Another entry in what you can call the Proto Harem Series: the books written before the Harem Series that take place in the same world.

It’s about a swordswoman whose student is captured, so she goes to rescue her.