Shiina Kazuya dies protecting two young girls and reincarnates as a young noble named Cain in a world of swords and magic. He's excited to be in a fantasy world, but then the gods grant him some insane protections and status...

Adventurers Millie and Nina arrive to be Cain's tutors, but they're overwhelmed by his insane status. His power with both magic and the sword is so great that they decide to train him outside the mansion.

Cain and his family leave for the capital. Along the way, they encounter two noble maidens beset by a horde of monsters.

Cain visits the church, where the gods tell him there's no entertainment in this world and ask him to invent some. Then Cain runs into Parma, an old friend who's training at her uncle's shop. So Cain asks Parma's uncle to help him create a certain item...

Cain has been named a baron and given a mansion—an old, dilapidated one. But with his magic, he's able to fix it up like new in no time, and he immediately starts preparing to host a debut party to introduce his mansion to noble society.

Cain finally reaches his twelfth birthday, the day he can register as an adventurer. He heads straight to the guild to sign up, but some older adventurers pick a fight with him, and he's saved by a red-haired man who looks very familiar...

It's the day of the Royal Academy entrance exams. Cain whizzes through the written exam, then heads outside for the magic and swordsmanship exams, but they don't go quite as smoothly...

Cain finds himself before Hirasawa Yuuya, the first king of Esfort. Yuuya tells Cain that the seal on the evil god Aaron is weakening, and Cain must fight him. Cain is hesitant, but then Yuuya tells him that Aaron is linked to Shiina Kazuya...

Cain must subjugate some bandits in order to advance to rank A in the guild. His handling of the quest makes his senior adventurers worry that he doesn't fit in at the academy, so they come up with a plan to help.

Cain finally gets to participate in a magic class, this time to learn summon magic... and he ends up summoning the Prince of Darkness. Meanwhile, signs of a monster onslaught have been observed in the Forest of Monsters.

With the help of his companions, Cain confronts Aaron and the horde of monsters attacking the town of Gracia.