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.

From his deathbed, Hero-King Inglis, the divine knight and master of all he surveys, gazes down on the empire he built with his mighty hand. Having devoted his life to statecraft and his subjects' well-being, his one unfulfilled wish is to live again, for himself this time: a warrior's life he'd devoted himself to before his rise to power. His patron goddess, Alistia, hears his plea and smiles upon him, flinging his soul into the far future.

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!

After a freak lightning accident zaps him dead, 15-year-old Mochizuki Touya wakes up to find himself face-to-face with God. “I am afraid to say that I have made a bit of a blunder...” laments the old coot. But all is not lost! God says he can reincarnate Touya into a world of fantasy, and as a bonus, he gets to bring his smartphone along with him! So begins Touya's adventure in a new, anachronistic pseudo-medieval world. Friends! Laughs! Tears! Inexplicable Deus ex Machina!

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!