Legend of Star Soul: It Starts with the Union of the Contract Machine Girls

Leo, a good-for-nothing boy abandoned by the Holy Light, finds Rell, a mech girl who falls from the sky. He forms a contract with her and transforms into the knight Evil Spirit, launching a legendary adventure.

Rell's home planet was a Level Two civilization, advanced in both magic and technology. One day, demons launched a surprise attack and destroyed it. She escaped through a portal, only to land by chance in the male lead's world, Seran, where civilization has only just reached the threshold of the First Industrial Revolution.

To stop his home planet from suffering the same tragedy, Leo sets out north with Rell, bound for the most technologically advanced nation on the planet. There, he hopes to build a “Doomsday Ark” and preserve the seeds of civilization before the demons arrive.

Leo grows stronger with every step of the journey. Though he sees the world's cruelty firsthand, he also meets companions who share his ideals, and together they embark on this epic adventure.