Blood Titan System

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! — Description from novelcodex.org