The Retired Hero is an Extra - Chapter 161 - : Limits Tested

In a world ravaged by radiation and the remnants of war, Dylan is far from a classic hero. A lieutenant with a tainted past, he's just trying to survive the ruins of a dying world... until the day he wakes up bound and surrounded by the mutilated corpses of his comrades.Captured by monstrous creatures, he soon realizes he’s been transported to another world. A world far more dangerous, far more brutal—where only the strong survive, and even monsters are hunted. Saved in extremis by Maggie, his commanding officer, he begins a desperate escape. Their only hope may lie in their encounter with Élisa, an elf abandoned by her kin, and their discovery of a mysterious power: anima gems—stones imbued with spiritual essence that can enhance body and soul, and unlock the path to awakening.No One under 18 admitted

The youngest Wiseman of the continent, Chu Tian, has traveled 30,000 years back in time to the age of antiquity due to an accident.

This is a prosperous era. Rare herbs, minerals, treasure relics and monsters can be easily found throughout the land.

However, this is also an undeveloped era. Communications, traffic, martial arts and technology are in its early stage of development. Prosperous cities lack lighting while its citizens are uneducated.

Our decisive MC using his future knowledge creates Magic powered light bulbs, magic powered telephones, magic powered cannons, magic powered computers, artificial intelligence, psyche internet. 30,000 years worth of knowledge allows him to create miracles and shine brightly in this era. Allowing him to conquer the land and sit firmly on the throne of the 10 realms.

- Description from Novelupdates

“How many people have you killed? How many families have you destroyed? How many towns and cities have fallen because of you!?”“I don't remember.”The villain whom the main character was destined to defeat at the end of the novel. That was who I had become.There was just one problem...“Why am I a teenager!?”“Why is there a school acceptance letter on my desk!?”

In order to avoid marrying an old man from the neighboring county, she must run away. The first time she escaped, the general entered the city, and she rolled and fell in front of him, no, she kneeled in front of him (really not on purpose). The second time she escaped, the general came to visit her house, and the general caught her (he must have done it on purpose). The third time, she was bruised and battered, almost desperate, and he came galloping and took her into his arms. (He was very well-intentioned.) The general said, ” Although I do not want to hold a favor to you, it is true that you owe me a favor.” So? 

 An Ruochen is unwilling to submit to fate and meets General Long three times when she runs away from home. She expects to get help from a powerful man, but she is involved in a secret conspiracy instead. Vicious family, a missing younger sister, a mysterious spy, and power struggles. An Ruochen becomes the key to solving the mysteries and becomes the core of General Long’s heart. 

One sentence synopsis: The right person at the right time changes everything.

- Description from Novelupdates