Supreme Casanova: Ultimate Harem System - Chapter 292: House Of Horrors.

“THE NEW GATE”, an online game that trapped its players and turned into a death game, was now releasing the thousands of players that had been dragged into it, thanks to the efforts of Shin, one of the most powerful players. But after having defeated the last boss and freed everyone, he was swallowed up by a strange light and found himself inside the game world 500 years in the future and unable to leave.

The world that nurtured the civilization which reached the pinnacle of magic was on the verge of destruction.
The last survivor transmigrated to the past, when the magic civilization started growing, as countless mages were still fumbling their ways through the thorny paths of magic knowledge.
He, who came from the end of the magic era, aim to reach the pinnacle of magic.

- Description from Novelupdates

18 years have passed since I was born as Allen, the eldest son of an earl in this world, while still retaining my memories of the present world. This world is peaceful and a stable society. The only extraordinary thing is that I was reincarnated into a world that is lenient on the existence of concubines. I selected a silver-haired maid as a sex slave and second wife candidate from among 10 candidates after a strict fellatio practical exam. I then lived an erotic life at home and at school as an attendant, but my reincarnated life is so fulfilling that I'm worried it will explode, as my busty childhood friend, a noble girl who was unsuccessful, ran for the third wife candidate, and my stepmother, who was my virgin partner, was sold off.

Mu Yue traveled to the world of Naruto and became an ordinary chuunin teacher at Konoha Ninja School and a member of the Root Organization.

Fortunately, after awakening the teacher system, you can become stronger by teaching.

In order not to become Danzo’s consumables, Mu Yue worked hard to teach and increase her strength.

“Complete the teaching rated A for the first time and receive the reward – mastery of fire attribute chakra properties change.”

“Under your guidance, Uchiha Shisui has worked hard to practice, and his overall strength has been greatly improved, and he has been rewarded – the Immortal Human Body!”

Under Mu Yue’s guidance, Zhishui understood that the village’s enemies were not necessarily other big countries, but could also be within the village. People who spoke righteously about the will of fire might not necessarily act in accordance with the will of fire.

Obito got rid of the title of being the weakest person in the ninja school, and Metkai became a master of physical skills even earlier…

- Description from novelbuddy