Re:Zero Kara Hajimeru Isekai Seikatsu - Chapter 86Arc 7, - “The Five Bastions”

She is a top-class spy, a poison specialist, but also a young and cute girl with a sinister temperament. In spite of her sweet and innocent appearance, she can complete any tasks without the slightest hesitation. One day because of an incomplete black magic, she was sent into the body of a girl who was deemed as a good-for-nothing. What kind of change will she bring to this continent?

A Prince said with bitter hatred, “I thought she was weak and easily bullied, therefore I broke off the engagement. I really didn’t expect she is such a shrewd girl. I made an error of judgment.”

The Crown Prince deeply sighed, “She is such a sexy evildoer! Obviously, she has a frail and tender body, but I am not able to overwhelm her…”

Finally, an Emperor hit the nail on the head, “She is just a bit two-faced!”

She answered, “You’re just a big pervert!”

The Emperor carried her into the room and said, “You are predestined to be mine! A two-faced girl and a pervert are a perfect match, right?!”

- Description from Novelupdates

Madeline Celeste d'Aumont is the first daughter of Duke Aumont and Duchess Louise-Marie d'Aumont who has been engaged to the Second Prince of Pays Des Abrutis since she was a child. The Second Prince decided to marry a woman closer to his own age and broke off the engagement to Madeline who was left with a broken heart and a reputation as being an unwanted woman even before she was an adult. The Duke decided to help his daughter regain her confidence and reputation by sending her to the Academy de L'échec.

Ito Aoi was the son of a Kendo master who ran a dojo in downtown Tokyo. One day while crossing the street to get some Yakitori, Aoi was hit by a delivery truck and woke up as the trash first son of Duke Montfort, Guy de Montfort. Duke Montfort also sent his son to Academy de L'échec only Aoi instantly recognized that he was now living in the world of an Otome Game that his sister loved to play and talk about all the time. Aoi recognizes that Madeline is the villain from the game. Aoi also recalled his sister saying that Madeline was terrible in the game, but is she really?

In this fantasy world, music and aether rules all. However, there is constant threat of demons and natural catastrophes. The most powerful men are musicians who use music, alchemy, and spells to safeguard their homes. A young man who just wants to find his father and know why his family was exiled, starts his journey of becoming musician – a journey that leads him to the crown of justice and glory.We are born of aether, grow under aether and die as aether. Awe of Aether! – Holy Code.

When she woke up, Lake returned to the classroom of the third year. The classmates were in class with swords and sticks, and the teacher became a female Taoist.
The little fat man in the back seat, how to put two big hammers under his chair.
Rick found this to be a global era!

- Description from Uukanshu (translated)