When a mental person in a normal live gets isekaid

Sinopsis: "what happens when a mentaly-questionable person in a SoCiEtY meets with the amalgamation of their previous self(or so ThEy say) that also happens to end all of existence once? Shenanigans happens. Lots, and lots of shenanigans.
so, if this absurd story interest you, get ready, because it will make you questions things you never thought to be questioned. If not, the go and read the stories of other people, it's not like I hold you at gunpoint to read this terrible story."
ps. Its literary my first story so expect a mother-load of cliché, cringe, and terrible writings. Critics and advise are welcome. And I am also the world worst typo, so keyboard warriors, have fun correcting me in the comment section.
also, the story will be a bit vague in describing something/someone(mostly because, again, first time writing, and also, I'm a bit bad at describing things in general), so use those imagination or whatever tool to help for a somewhat clear picture of things.
obviously all story rights are reserved towards the original owners. i own nothing, as this story is a fanfiction of sorts. the plot and mc are mine, but everything else do belong to the original owners in some way, shape, and/or form. i may not know be the makers but i sure as shit going to give them credits and rights as the original owners, so don't say i never said it.