MTL - Within Ten Meters, Fly In Situ - Chapter 109 "You need to exchange it with your spiritual root."...

An alien race invaded the Earth on June 6, 2128. At the midst of this war, many nations allied with the alien threat and the war nearly wiped out the rebelling humans of the planet. At the edge of mankind's survival, the United Nations Army launched its forces to eliminate the immediate stellar threats that loomed over Earth.

General Seeker Carlean, commander and leader of the mission, risked and gave his life to destroy the immediate stellar threat. The battle was won though Earth lay in ruins. Perhaps mankind will live to see a few years of peace before the alien threat returns to wipe out their existence.

At the immediate aftermath of the stellar battle, the fallen Seeker Carlean awakens and finds himself at aged 17, living the peaceful life he lived 16 years before he died.

So begins a new game in the battle for humanity's survival.

Divorced, disowned and down on her luck, Shui Anluo was determined to move on and live a peaceful life… That is, until her ex-husband somehow managed to find out about her baby. Now, he’s insisting that she should move back in with him. Soon, he realizes that he cannot live without her… But the road to marriage is bumpy, and Shui Anluo isn’t too willing to go through with the heartbreak again. Can she take back everything that belongs to her? Will she find the courage to jump in and fall in love again?

This legend tells the tale of the protagonist, Kuroki summoned to protect the demon king from the hero.

Kuroki, unbeknownst to him, suddenly came to another world. He was summoned by the demon king, Modes. The territory which the demon king overrules was in the midst of being destroyed because of the hero. He had no choice but to bow before Kuroki.

“Please save us, Savior Dono!”

Kuroki nodded, deciding to save the demon king due to an unexpected turn of event.