Martial King's Retired Life - Chapter 48Book 15:

The world where the Hero and the Demon King continue to oppose each other. The grand magic from the Hero and the Demon King cross over worlds and exploded in the classroom of a certain high school.The students who died in the explosion will be reincarnated in a different world. The protagonist, who had the lowest reputation in the class, was reincarnated into a spider. Nevertheless, she adapted quickly to the present condition with strong willpower.This is a story of she who has become a spider trying whatever she can to live.

In a tyrannical world, what is evil? What is benevolence? All living creatures are brutal. Passing through the heaven road to find one’s purpose in life. Struggles to be stronger is not an easy path. The whole journey thistles and thorns, one blade chops open a path, I alone will be supreme!

Xu Mo, a modern high school student was sent back in time to Jing Kingdom and found herself trapped inside of the body of a princess with the same name.

She had barely recovered when she learned of an unparalleled fiancé and in a daze, they got married. Then the stunning genius physician who normally does not pay attention clamoured to marry her. After that, there was a cold general, a flirtatious lord, a tsundere young master……

As it turns out, this was a male-dominated dynasty. Because the female population was sparse, the entire nation shared wives regardless of rank or nobility. Is it feasible for someone who wants to maintain monogamy in this dynasty?

- Description from Novelupdates

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.