Zither Emperor - Volume 1 Chapter 3

When The Cute Kunoichis Spied on Their Teacher's Secret is a light novel written by Kazuma Kamachi and illustrated by Ryuushi Tajima.

The story takes place in a world where Japan never ended their isolationist phase, and agents from foreign powers are always threatening to steal the country's advanced technology. In order to combat this threat there has been a resurgence of ninjas that use Strategic Martial Arts, techniques that combine cutting-edge modern technology with a traditional foundation of martial arts and ninjutsu. The story follows Souha Sugiyado, a 17-year old ninja instructor and former ninja prodigy who was forced to retire from active duty by the wounds he suffered in his last mission. Souha's four students are all kunoichi who have all gained the rank of Elite Ninja, the highest official rank available to ninja. However, one day two Shogunate ninja approach him with the news that his four students have gone rogue and have stolen a portable modular nuclear reactor, and thus they ask for his help in bringing his students to justice.

“You mean that Prince Yu wants to marry me?”

“Exactly, young master, Prince Yu wants to marry you!”

“Hell no! Is he out of his mind? Even if woman is a rare species nowadays, as the prince, he could have a chance to marry one. Is it because he got excluded, or maybe he has sexual impotence, so he could only marry a man?”

“No, Prince Yu is charming, majestic, endowed with civil and martial virtues, and also in perfect health.”

“Then why would he marry me?”

“Maybe because of your reputation out there.”

“Reputation? Am I quite famous?”

“Of course. Young master, you’re far-famed.”

“Really? What did they say about me?”

“They said you are ugly, good-for-nothing, short-lived, a freak, with no morals, and shameless…”

…

- Description from Novelupdates

10 years ago, after “the Gate” that connected the real world with the monster world opened, some of the ordinary, everyday people received the power to hunt monsters within the Gate. They are known as “Hunters”.