Death March kara Hajimaru Isekai Kyusoukyoku (WN) - Book 17 - Chapter 17-13. Changing World 2

The two faced number one female spy transmigrates to a different world and becomes an outrageous idiot girl. When she woke up, what she had to face was consecutive blows of the decline of her family clan, her crippled martial skills, and her disfiguration. To protect her family, she must obtain the treasured book, obtain outstanding achievements, summon a dark beast army. Wait and see how in this unfamiliar, dark magical continent, she dies and becomes a demon then steps up to the top, making all of the formidable people in the world bow down to her in respect.

- Description from Novelupdates

The maniac who was crazy about all kinds of fields such as military and steampunk had been reincarnated.

However, his father was King Sejong the Great?

The mania-wise king and his crazy maniac son.

Along with the ministers, and countless humans who were getting exploited.

Even today, the night of Joseon was filled with the light of overtime.

(Immortal Cultivation+Meeting a Perfect Match+Shura Field+Invincible Flow+Upgrade Flow+Playing the Pig and Eating the Tiger)—What is cultivation? When I think back to the past, cultivation was, as a baby, kicking my legs over and over again—kicking on the bed, kicking on the ground, kicking every single day. Cultivation was, as I grew older, swinging my sword again and again—slashing here, cutting there. Cultivation became, as I matured, the repeated harmony of yin and yang—busy tonight, and busy again tomorrow night. … My name is Xu Ming. I have never cared about the stipends given to me by those sect masters, noble ladies, or princesses.I said to her, “Can you give me a room closer to yours? I need to report my work to you at any moment.” Even if I accomplish nothing every day, I just want to watch how she cultivates. I…

“If you were the supreme master of the Dao of Immortals, revered by countless beings, able to glimpse life and death, and understand the destiny, what kind of woman would you seek as a partner?”Jiang Feng: “I would marry an eighteen-year-old.”“...do you want to die?”“I'd rather die to marry an eighteen-year-old.”