I am a Gao Fushuai Villain - Chapter 576:

On her wedding day, she was humiliated; her status as the legitimate wife was instantly changed into that of a concubine.

Eren Idril died as an old, decrepit, and piss-poor adventurer by the maws of a D-Rank monster. He had a lot of unfulfilled dreams and desires that couldn't see the light of the day after the light in his own eyes died down.

But fortunately for him and unfortunately for the world, that wasn't his end. Eren was somehow dived back in time when he was a mere teen, attending Lionheart Academy for adventurers.

When life gives him a second chance, Eren decides to exploit it to its fullest. Experience his vile deeds as he partakes in them without feeling the slightest bit of hesitation.

A fickle, decadent, wilful person going through life like it’s a game.

An experienced, logical mind that’s above feelings.

This was a relationship that had started off with “Carpe Diem”, but slowly turned into a bloodless, psychological battle. They shared a mutual distrust, but also mutual attraction. As they suspected and tested each other, challenging each other’s limits, they both fell into the enemy’s hands with their eyes wide open. Sentiments growing amidst ignorance, they finally, were caught in their own traps.

Winner takes all,

Loser stands small.

- Description from Novelupdates

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.