Fairy Tail: I Stole the Ryujin Jakka in My Sleepwalking - Chapter 81: FTRJ -

Mortimer Zhu is an extremely unfortunate high school student who accidentally enrolls into an academy of a dubious nature, where it is the norm to jump in front of moving trains, get dismembered during orientation, and crushed by vindictive bouncing classrooms. Can he stay alive or will he die from the rigors of school? Why have evil spirits suddenly acquired a taste for his flesh?

- Description from Novelupdates

​The world, Earth, was devastated by the Great Incursion, an apocalyptic invasion by dimension-hopping monsters. Humanity's only hope now lies in Galaxy Fall, a newly accessible parallel world where they can gain strength through a System of quests and missions.​Five hours after the Invasion, the betrayed survivor Mirabella is mysteriously reborn and gains a unique power: the [Master Account System].Her initial skill is the deceptively simple but devastating 'Multiplier x100', which applies a 100 times buff to all her offensive capabilities, including physical attacks, spirit energy skills, and damage-over-time effects.​Mirabella must now transform from a silent survivor into the world's most feared warrior, who was only scared of one thing, which is?“I Hope I don't run out of opponents in Both worlds.”

Synopsis below:How did the Avatar universe change when a transmigrant appeared in an unknown village, long before the canonical events? And how are the two islands Kyoshi Island and Uzushiogakure no Sato (A village hidden in the maelstrom)?---Tags: AU, Before-canon, Post-canon, Violence, Death of major characters, Transmigration, Harem, Children, Incest, Romantic. Foul language.