QT: Against My Will - Chapter 35

Oosuki Masato is an ordinary high school boy who is magically transported to an alternative world, but for some reason his doting, over-protective mother comes along as well.

The first great emperor in the world was betrayed by his confidante and perished. Millions of years later, the great emperor’s soul returned and was reborn as Ye Yan, the son-in-law who was kicked out by the Chu family with a letter of divorce, restarting the supreme journey. Open the gate of immortality, kill the Jiuzhongtian, and cast an invincible name again!

- Description from novelbuddy

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.

The male student, Fukai Nagamasa, ignores his studies for college entrance exams in favor of following the path to chuunibyou. As he fainted during night cramming session before the exams, he realized that he was transported to a parallel world as a feudal lord in the Sengoku Era. Not to mention that suddenly, he was marrying the sixth Demon King, Oda Nobunaga’s little sister, the one who was purported to be an unrivaled beauty?