My Classmate is 200 Million Years Old - Chapter 30

A martial art expert from the Song dynasty lives like a Phoenix that can live again in another body after death. This time, he happened to take over the body of a Japanese high schooler who is also a victim of bullying and has a bit complicated family circumstances.

- Description from Novelupdates

Masterpieces such as 'The Divine Comedy', 'The Theory of Evolution', 'Encyclopaedia Britannica', 'The Theory of Relativity'...Born in the history of human civilization, possess mysterious and magical powers in another world!Original sin, biological evolution, mastery of all arts...By reading the secret tomes, one can gain a variety of powers!The only trouble for the people of the other world is that they find it difficult to understand the texts from Earth.At this time, there comes a librarian from Earth...

“One Generation Immortal Venerable” Luo Chen was attacked and reborn and returned to Earth.

He is an ordinary person, facing the contempt of his girlfriend, the ridicule of his rivals, the miserable life of his parents, and the threats and provocations of the rich and young.

He vowed to change the injustice of fate, stand on the pinnacle of this world, and tell everyone that Luo Chen had been here.

- Description from MTL

The second prince has come of age. To celebrate the advent of such an occasion, the search for a suitable bride began. My younger sister was expected to go to the Royal Palace as a candidate. However, despite this, she eloped the day before her departure. I, the older sister she left behind, looked almost exactly like her – so much that we were often mistaken for twins…

One month, right? For just one month, shall I substitute in for my sister?