Been reading this OMORI fanfiction called “This might as well happen” by Strawbits on Ao3 and it’s gold.
It’s plot takes place after a few months post the Good true ending, and Sunny has suddenly received Omori’s powers. Shenanigans happens, and all’s goodish until his friends come into the picture. Then it gets difficult.
Anyways, if you haven’t, I highly recommend reading it! It has art for some chapters, as well as great humor and Sassmori.
I also headcanon that when Omori takes control of the body, he has this dead expression in his eyes.