Tensei Shite Inaka de Slowlife wo Okuritai - Chapter 4 I want to use new magic

In a world teeming with Titans, Colossals, Gigantic Monsters and Kaiju's, Erian who reincarnated makes his living collecting scraps of low-grade Defective Genetic Serum, realised he transmigrated along with his system.

Follow Erian as he grows to become the strongest Disaster Grade Titan with the help of his Titan System!

The notorious imperial court lackey and the meritorious military general were well-known for their mutual dislike, a pair of arch-enemies set in stone. Who could have foreseen the unexpected change in the winds of heaven: the general injured on the battlefield, both legs disabled, and even forced by the emperor to marry his nemesis.  

With one marriage edict, two people with mutual hostility are forced to marry and live under the same roof. Yet after these long days together, they come to the realization that this fellow is not truly devoid of any saving grace/unattainable and high out of reach.

- Description from Novelupdates

The only being with extraordinary powers on Blue Star has mastered the Gatling Flight, turning missiles into flying swords. His short-term goal is to destroy planets using psychokinesis.

After being transported to this world, Nara Kazuki discovered that as long as he grinded enough proficiency, his jutsu could level up.And so, he began walking a very... peculiar ninja path.