First Day In Game, I Got Ten Billion From Infinite Number Of Check-ins - Chapter 339 - Go in Peace

Xin Yun, a sarcastic young man, traveled to an unknown world by chance, but lost his chance to become the strongest because of his obsession with women... or sex. In a collision of the powers of nine powerful men, an incredible thing happened. Xin Yun was reborn back to the time when he traveled to the Isekai world. A fantasy journey is about to begin... [The comic adapted from this novel is popular all over the world]

It begins on the mountain.

With the glint of a knife, a flash of steel in the hands of a sworn brother. A betrayal.

Stabbed and pushed down the mountain, Zi Chen lied within the red-stained snow, left to die.

This is where it begins; he is given life by lightning,
baptized by thunder.

Those who had once betrayed him should all suffer in his cruel revenge.

- Description from Novelupdates

Dewitt, known as the Iron Marshal, is now on the verge of death. Just when the whole empire thought he was not going to survive, a small fox came down from the sky. The little fox was so powerful that it woke up the Marshal who had been in a coma for a month with one paw. If Wen Jin knew that the price of his paw was to become the Marshal’s fiance, he would refuse, because the legendary, ferocious Marshal was a well-controlled villain, only touching his fluffy body every day.

Wen Jin: You’ve had enough, I’m going bald!

Dewitt: Ten more minutes.

Wen Jin: Not a minute longer!

Dewitt: Then let me kiss you.

Stupid and lazy fox x black-faced Marshal meet in a world full of Zergs and war. Follow this intergalactic tale as they begin to trust and depend on one another.

- 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.