MTL - Fairy Tail: Start To Capture the Fairy Queen Erza - Chapter 411 God Serena? It's just another exclusive weapon

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!

Many islands dotted the vast oceans of this world. However, some of the islands were a lot more sinister than the rest. Those islands, known as Nightmare Islands, were true nightmares to all but the strongest and most fortunate. Children were kidnapped and thrown on these isolated islands by the Nightmare Palace, forced to sign soul pacts with evil soul pets: Nightmares. These devils slowly devoured the souls of their trainers to grow stronger. If the children did not cultivate fast enough, their souls will be devoured whole, leaving only an empty husk behind.

Chu Mu, the protagonist, was an heir to the Chu Clan, but due to a plotted murder, he was thrown on the island, sentencing him to almost certain death. Dancing on the edge of life and death, he struggled to survive with a small Moonlight Fox he captured. When he finally escaped the devilish foremen on his island, he couldn’t help but let a breath out. But little does he know, the experience was only a beginning to a fated journey with his little Moonlight Fox…

Liu Duo was a young girl whose grandmother sold her to four brothers with the intent to be a bride. Unwilling, she ran away the following night, only to fall unconscious while trying to get away. Unexpectedly, however, she was reborn with the spirit of a 25 year old woman, also named Liu Duo.

- Description from Novelupdates

I finally managed to kill the demon lord.