Owari no Chronicle - Volume 11, Final Chapter: Destination of Prayer

One day, Luo Jian woke up from his sleep and found himself in a locked chamber where the door and window were all sealed. A note with a few lines written on it was tacked to the wall: “Escape from this room within an hour, otherwise, you will die.”

There is a sequel called Reincarnation Night (轮回之夜) that takes place in the same universe but has different main characters

- Description from Novelupdates

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 are the ruler, I am a subject, you want loyalty, I’ll give you loyalty. You are the ruler, I am the subject, you want my sacrifice, I will sacrifice for you. This lifetime, we’ll only be ruler and subject…… cannot become the one who accompanies you to experience everything.

A deposed empress, a failure of a substitute. Charging into battle, he was the emperor, and she, his general. But within the intimacy of their military tent, he was her husband, and she, his wife.

But everything was star-crossed. For the one he loved the most, he would push her into hell again and again.

- Description from Novelupdates