MTL - Final Redemption - v16 Chapter 3 Military fortress! 7th

An angel made a mistake, resulting in Shiihara Daiki’s death. In order to hide the mistake, he was then sent to a different world. The angel will grant him one wish as a payment for keeping it a secret. Daiki asked for a Heavenly Castle floating in the sky without hesitation.

Suddenly a floating castle appeared in the new world, which causes confusion amongst the people. They attempt to contact Daiki in various ways. A country tries to steal it by force, while another seeks to befriend him. What in the world would Daiki do?

Bai Aoxue, the best mercenary in the 21st century, is accidentally sent back to the Chengxi Dynasty in Great Continent due to an explosion in her mission, and trapped in the first daughter of Prime Minister. After her rebirth, she is set up by her father to marry the 5th prince Jun Yeyan who wears a mask all day long.
In the face of bloodthirsty enemies, discord between brothers, collusion among courtiers and invasion of enemy state, can Bai and Jun resolve the crises? What will happen to their political marriage? How will the fierce battle for the throne end?
With many twists and turns, the book brings you to experience palace revolution, love and hatred thousands of years ago.

- Description from Novelupdates

In the residence of the Duke of Zhenguo, the legitimate young miss, known for her icy demeanor, had transformed overnight.She, who usually regarded no one, woke up to confront anyone she saw with a few harsh words, using her frail body to intimidate so much that no one dared to touch her.Afterwards, this legitimate young miss began taking on retainers, nurturing powerful officials, engaging in commerce, and recruiting troops… Every act so shocking and audacious, it defied the norms and provoked fear in all who spoke of her!Yan Wanqing was seen as an enchantress and a disaster by the people, a thorn in the flesh and a nail in the eye that the ministers wanted desperately removed, an entity everyone shunned as if she were a venomous snake.Only the Crown Prince Mingyue, descending from the divine altar, in the dark, godless alleys, grasped her neck and repeatedly asked her, “Will you marry me or not?”

It has been more than ten years since he was transported to another world. The protagonist Deris Fahrenheit, who has became a magician with special circumstances, was freely enjoying his life in this world. However, a girl appeared before him and asked him to make her his disciple. That girl seems to be a transported person――

It’s a story of him who becomes the girl’s teacher and trains her to achieve her revenge (?) in otherworld.