Death March kara Hajimaru Isekai Kyusoukyoku (WN) - Book 2 - 2-7. Demon Return

This world is not reality, nor am I the protagonist.

Ye Xiwen was previously only an ordinary university student on Earth, but unexpectedly crossed through into the world known as the Zhen Wu Jie world! In this world, formidable warriors are capable of turning over mountains and collapsing the ocean, destroying the sky and extinguishing the earth! He originally had ordinary aptitude, because of that he received the mysterious special space! Any martial art can be deduced within the mysterious space, other people practice for decades, he only needs a year! So long as he has enough spirit stones, any talents he faces are all floating clouds!

- Description from Novelupdates

Monica Everett, a genius magician, was extremely shy and terrible at speaking in public.

To that end, she worked hard and mastered the art of countless magic, which she could use without chanting. After being chosen as one of the Seven Sage at the tender age of fifteen as the “Silent Witch,” she lived a quiet life in the forest.

However, two years have passed since then, and one day, Monica received an order.

And it was to secretly protect the second prince to the academy undetected.

In order to protect the prince, Monica must infiltrate a glamorous school for the children of noble families.

“I don’t wanna do this… I’m scared… Ugh… My stomach is aching…”

…said the girl whimpering.

Cho Kang-hyuk, the owner of a large fitness center, woke up to find himself a young disciple at Shaolin Temple.