MTL - After Wearing the Book, I Became the Second Mary Sue - Chapter 34 "repay"

Once a regular high school student, the protagonist gets sent to another world via truck. He reawakens to find himself contracted to a girl about the same age as him before passing, and that his body was no longer that of a human. Given a new name as the girl's contracted spirit, he spends his days at her side._ _ _ _ _ _ _ _ _ _ _This is not a novel I will be updating multiple days a week. The most likely outcome is me updating it once a week, but if any readers would like to read my other works, I would like to suggest reading the story I update most which is “Level One Isn't Weak!”.

“A cheat system? Do you take me for a fool? Nowadays, where can you find such a good thing falling into your lap? Scram from my head. Is this is new kind of fraud? Or is this a murderer training system of aliens that contains the ability of hypnotism?”

“No, I am the chaos that whispers from nothingness, the nightmare of all living beings in the Southern Ten Stars, the successor of the unparalleled God and… your elder sister.”

“…I only have a younger sister, I don’t have an elder sister!”

“No, you have one. I am an illegitimate daughter. It’s just that your dad didn’t inform you.”

- Description from Novelupdates

Born with the fate of a slaughterer, but all he wanted to do was help.