Third season of the Monogatari Series, part 5/5. Contains the arc Koyomi Reverse from the Zoku Owarimonogatari light novel.
 
The morning after high school graduation, Koyomi is standing in front of the mirror above the sink to wash his face when he suddenly feels like his reflection is staring back at him. He instinctively reaches for the mirror, and upon touching it, his fingers sink in... When he comes to, Koyomi finds himself in a world where everything appears to be reversed.
 
(Source: Aniplex)
 
Zoku Owarimonogatari premiered in theaters across Japan in November 2018. It was later released as a 6-part OVA on Blu-ray/DVD from February to March 2019.