A certain college girl who's loved books ever since she was a little girl dies in an accident and is reborn in another world she knows nothing about. She is now Myne, the sickly five-year-old daughter of a poor soldier. To make things worse, the world she's been reborn in has a very low literacy rate and books mostly don't exist. She'd have to pay an enormous amount of money to buy one.

Beautiful and brilliant sorcerer girls just can't have nice things, huh? All I wanted to do was swipe a little bit of bandit treasure. Now suddenly I'm being chased around by icky trolls, nasty demons, mean mummies, and brooding golem bad boys. And for what? A tiny little artifact that can bring about the end of the world? Hah! I'll show them there's a reason you don't cross Lina Inverse...

Sagara Sousuke isn't your typical high school student. He reads military enthusiast magazines; he responds to questions with "affirmative;" he brings grenades to school in his bag. Though everyone at school takes him for a hopeless military geek, Chidori Kaname thinks there might be something more to him. When their plane is hijacked in the middle of a field trip, Kaname's instincts will prove correct: Sousuke is an elite, mech-piloting mercenary... and he's here to protect her!

One day, the life of middle-aged Japanese businessman Ryoma Takebayashi came to a rather sudden and disappointing end. Ryoma had never had a blessed life, but after his death, three great gods sought his cooperation and reincarnated him as a child in another world with swords and magic!

Ryland Grace is the sole survivor on a desperate, last-chance mission - and if he fails, humanity and the Earth itself will perish. Except that right now, he doesn't know that. He can't even remember his own name, let alone the nature of his assignment or how to complete it. All he knows is that he's been asleep for a very, very long time. And he's just been awakened to find himself millions of miles from home, with nothing but two corpses for company.