The Black Book: Seven Deadly Sins - Chapter 24: There Are Still More Good People in This World

A girl who calls herself a demon appeared before a timid student named Fumio Kijima. The girl claims to be a campaign girl from the demon world and she gives him the ability to “summon a room” from nothing but thin air.

At first he doesn’t abuse his power and uses it as a convenient ability in his every day life. But one day he is bullied by his classmates under a false pretext and is made to suffer. In the past he would have wallowed in misery and cried himself to sleep, but now he had a power to call upon.

“I will make them regret it!”

Using his powers to summon his “room”, he begins his era of confinement and brainwashing to achieve his goals.

An otaku with a hobby of masturbating was reincarnated as the son of a great mage.

As soon as he was born in this life, he vowed with a goal of embracing women till his death.

That said, when he became 20 years old, the Demon Lord which was sealed by his ancestors revived, and now it is his role to seal it once again.

And that demon lord is sealed in a tower dungeon that is rumored to be impossible to capture.

However, by an unexpected coincidence, he had found out that the Demon Lord is also one of him, a kindred spirit from within,

so he joined her instead and filled several traps in the tower dungeon, and thus they enjoyed a s*x spree with all the women coming over!

In the previous life, she was a swindling charlatan who had neither learning nor skills and was beaten to death.

Upon opening her eyes again, she had returned to when she was five years old. An impact from a clay Buddha opened her divine eyes, gave her photographic memory, astonishing talent, ability to view another’s past, able to sever the ties of disaster and fortune of life and death, a heaven defying rejuvenation technique, and a technique to recognize treasures.

In the last life, her family became ruined and she ended up a homeless wanderer.

In this life, she will defy heaven to change her fate and take back her happiness.

In the last life, she had nothing, had no education nor skills, was despised by others, and was looked at with indifference.

In this life, she exerts herself to become a real master of metaphysics, stands in the summit of the world, became a legend in the business world, sought after in the political circle, and a VIP of the underworld……

Those who owe her, all will be given one’s due!

He, like a deity who shows disdain for the world not only treats her with familiarity but also guards her like a loyal dog.

Her life became an unprecedented and unique existence.

- 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.