Monroe - Chapter Three Hundred and Eighteen. B-B-Boss Battle!

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.

The unparalleled Demon King Ye Xuan, who was able to heal the death or the living alike and holder of the medicine Holy Scripture, was betrayed and killed by his fellow Demon Kings. But he reincarnated into the body of Ye Xuan, the prodigal son of the Ye family and vowed to himself that he would return to his peak and take back everything that belonged to him!

- Description from Novelupdates

Wealthy, powerful and handsome; Gu Jingze is the cream of the crop in the entire country. Every guy wants to be him and every girl wants to be with him. His life is perfect… except that he has one tiny secret that keeps him from getting close to any woman—apparent impotency.

That is, until he wakes up in bed with a total stranger one day. The next thing he knows, he is forced to marry this stranger; a feisty and boisterous woman by the name of Lin Che.

Lin Che is an average girl whose only aim is to become a successful actress. Ostracized by her family and forced to become independent, she cooks up a scheme to attain her goal. But her plan fails and she ends up marrying this cold and seemingly heartless Gu Jingze. Not only that, she must now find her place in high society, where jealous women and devious plots lay abound – all while juggling her new career.

Two strangers under one roof: From the outset, they agree to stay out of each other’s lives, but he somehow always manages to appear during her moments of crisis. Slowly and unwittingly, Lin Che begins to find it difficult to imagine a future without him. Will their relationship grow, or is their marriage destined to remain just a contract?

- Description from Novelupdates

When Ye Qing Ran wakes up, she finds that she has transmigrated into a book. She has become the vain, domineering, and evil villain who dies a tragic death.