Everyone has (or has had) a reflection, but Ink has never had one.
As far as they know, anyway.

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Everyone has (or has had) a reflection, but Ink has never had one.
As far as they know, anyway.
So I wanted to make an au based off of "the splitting" games in which the reflections we see in mirrors are actually a glimpse into a flipped "mirror world". Living beings are prevented from entering or interacting with that world by their reflection's existence, sort of acting as a barrier, keeping them from crossing over.
The reflected person is unaware of these things, they simply see and experience things through the eyes of the person they're the reflection of.
But sometimes, a person and their reflection get desynchronized. They "split".
And the reflection becomes aware of their existence for the first time.
(and then i thought "but what if undertale multiverse")