Keeping Your Character by Insanity-Red is fantastic SI-OC fanfic(☆▽☆). It’s totally so much different from Russian Roulette: Reloaded and Lucky Child but like the different kind of good.
However, this story are lacking(or technically speaking in less details) in world building (despite the already explanation or excuses in later chapters it give in KYC) and power mechanics (also told in rounder manner). It does makes up for reasoning and psychologist of the characters(there are flaws but can be overlooked) and humour
Summary: When a girl from our world take advantage of a quirk in reincarnation system, guess who body she ends up in? See what changes when the stupid cow isn’t stupid-nor a cow. What will change when she retains knowledge from her previous world.
The summary quite suck I know but the story definitely better than that. Trust me.