MTL - Custom Made Demon King - Chapter 33 Is there a main theme

Because I like to collect antiques, I was accidentally brought to a magical world by a crystal skull in my collection.

- Description from novelbuddy

After a catastrophe swept across the world that destroyed half of the population and countries, a mysterious force passed through the earth that affected all residents, plunging them into unconsciousness for several hours. No one knew what it was.A few lucky people have received the revelation that the world will be destroyed in ten years. During these ten years, the world is waiting for ten disasters, and the last of them will be the end of the world.Another group of people also received a revelation that salvation is in another world. This revelation opened the way for them to another world where they could find solutions to save their home world.The rescuers were young people who were not yet twenty years old. They became awakened, able to transcend the boundaries of worlds.Idan was not among the chosen ones who became awakened. However, luck smiled on his older sister.A year after the world experienced its first disaster, Idan accepted an invitation to attend a grand ball dedicated to overcoming the first of the ten disasters.That day, during the ball, he met a young girl, and some mysterious force chose him. He awakening a mysterious system—the Supreme Husband System. In turn, the girl also received her own system — the Supreme Wife System.And so, the first task he received from his system was to propose marriage to his future wife within one day!English isn't my main language, so please bear with it if you found some mistakes.

Yeho is a distant relative to a king in a small kingdom. Even though he is a distant relative, his house was very poor, and his mother was addicted to gambling. One day North Empire asked for Princess Sooyoung to be a concubine of an old Emperor because she was known for her beauty. But the king really loved his daughter so instead he ordered Yeho’s older sister to disguise as Princess Sooyoung and marry the old Emperor.

Yeho told his sister to run away with her lover, and his sister had to leave her younger brother alone with his mother. After she ran away, Yeho asked his mother to give the things back to the king that she got for trying to sell her daughter, but his mother already used the gifts to pay off her gambling debt. He was trying to give the gifts back to the king to take away his order, but now he can’t do that anymore. He tells his mother to run away, and he disguises as his sister to go to North Empire.

After he got there, he was trying to tell the Emperor the truth and take away his life, but the Emperor went out for few days to look around his empire. When the emperor came back, he wasn’t as old as he thought.

What would you say is the most valuable thing in this world?