Tatakau Shisho - Volume 8, Chapter 4: The End of the Liars – Part 3

While reading a book, a sparkle of light disappeared. And, as it did, a message appeared.

In her last life, she was miserable and ordinary. This time, she got into the fashion and was reborn in another world. She was still the same person… even with the same body and face. What was the point of reincarnation? A childhood companion? He always pulled her hair and made troubles for her? A handsome boy? The boy never looked at her and was 15 years older than her! A prestigious teacher? The teacher spent his days eating and drinking, coaxed, played tricks, and controlled others… Too scary and better run away? No no no, such a challenging life was bound to be wonderful! Now let me take you back to the 70s and live a fast life!

- Description from Novelupdates

As the ruler of a munitions empire, Tang Mo unexpectedly fell and was transported to an entirely different world, where he also unexpectedly acquired a “King of Munitions” system.In this underdeveloped world, Tang Mo relied on the abilities granted to him by the system to drive the development of the entire world.After all, the desire for civilization conquest had always been the driving force behind progress, and life had continuously evolved between attack and defense over tens of millions of years...So, selling assault rifles to these archers and training knights to be tank operators... there shouldn't be any problem with that, right? XD

An ordinary (?) grandfather, Choi Chuntaek. In an effort to protect his granddaughter, he started the virtual reality game 'Arkstar.'

Then... he accidentally obtained a legendary class?