MTL - Martial Arts Master - ~ Festival has been more)

Legend says, that there is a great demon, who is the human kind’s public enemy. He is the galaxy federations’ nightmare as he wanted to conquer the whole universe. On the first day, he completely took out the human fleet, plunging them into disorder. On the second day, he declared that he will wipe out the whole federation. On the third day, he declared——that the hero who shot him in their previous battle must marry him, or else, he will destroy everything.

The galaxy federation president and the council members had a long meeting after that. They decided to dispatch a soldier, Wu Xing Yun, and marries him off to the arrogant demon. Wu Xing Yun was once a hero who fought for the nebula, and henceforth, he was tasked—— for the sake human race and the universe’s peace, to eliminate mistresses, settle his matters with the mother-in-law, and fix the man’s crooked ways.

Wu Xing Yun was very perplexed when he asked his commanding officer: “Sir, why did it have to be this way?”

Commanding Officer: “Soldier, bear in mind, that this mission of yours, is for the sake of the universe and mankind’s happiness. You must hold on to your husband, and fight other mistresses! Do you have the confidence to accomplish this task?”

Wu Xing Yun, stood straight, saluted, and instinctively replied: “Sir, yes sir! I will accomplish this task!”

- Description from Novelupdates

Every family has that one person who is born as a sacrifice. For her family, that person was Selene Vale, who was to become a spare for her younger twin siblings success.Due to her innate shy and kind nature, she was not able to connect to her family every since she was young. So, despite her rich background, Selene Vale never felt like a part of the family and was often regarded as the 'First spare' or even 'defective'. That did not change even when the world fell and Apocalypses happened.Selene Vale's first life ended trying to protect her twin siblings, the only people who had yet to abandon her. That was her end......but it wasn't.Due to her sacrifice, Selene Vale awakened her system and innate power and was given another chance at life and survival. And this time, she vowed to free her siblings from their parent's cruel influence. If she was able to do that, then she would be happy with that.But unfortunately, that was not all she did. She also ended up attracting the attention of the big-boss of the Apocalypse, the only L-ranked hunter and the hope of humanity....and also, a long time friend she would rather forget about.