Toaru Majutsu no Index - Volume 10, Chapter 8: The Reason for the Clenched Right Fist. Light_of_a_Night_Sky.

Three years ago, the animals and plants on Earth underwent crazy and unexplainable changes that included transformations, reversions, and the addition of otherworldly species. And it was the start of a brand-new type of profession in the new generation of humanity – Monster Trainers, people who specialized in taming monsters.

I, an ordinary high school student, Kimizuka Kimihiko, who easily gets involved in things, was appointed to take care of mysterious attache cases by mysterious men in black suits. After meeting a beautiful angel-like detective girl, named Siesta in a hijacked plane, I became her assistant.

And from there–

[You deal with the beehive, and I’ll restrain the enemy.] [Don’t make plans that make me the victim.]

We had those kinds of foolish conversations, all while being completely broke every day and fought against . Even when there were hurricanes, the weather-beaten duo sleep past it. Sometimes when we saved money at a casino, we would jump around on the beds at a resort hotel, only to be broke again the next day. We would walk through deserts, traverse through jungles, conquer mountains, cross oceans– The great detective and her assistant would go through these dazzling adventures–

Until she died.

And this story starts from 1 year after that incident.

I’m the only one who’s left, but I carry on her remained wishes.

This story is far from over..

He had crossed into the dark, ruthless Wizard World.Lucien found his system somewhat different from the usual golden finger.System upgrade points? Chip activation?None of these, but rather becoming a role model, transforming into a nurturing breeze:Teaching students knowledge, receiving advanced knowledge in return.Caring for and maintaining students, earning generous rewards.[Your student has mastered the Magic Potion “Kuru's Cough,” congratulations on acquiring the improved formula “Kuru's Cough - Enhanced”!][Your student has mastered witchcraft “Fireball,” congratulations on learning witchcraft “Greater Fireball”!][Your student has successfully crafted the wizard's tool “Pale Mask,” congratulations on acquiring the wizard tool’s manual “Revised Pale Mask”!]Initially, Lucien was resistant.But after experiencing what it was like to teach disciples and outdo them, Lucien felt he had completely transformed into the form of the master system.This thing, isn't it much more useful than something called Cheating Device?

Chu Guang, who had traveled to the post-apocalyptic world, discovered that he had unlocked a shelter system and was able to summon creatures named “player” from the previous world.

From that day on, the whole post-apocalyptic world became like a game.