When Adachi was revealed as the killer in the game and the original Animation, he was pretty creepy. In this anime? We get a whole episode exploring his twisted psyche. This shot◊ ups the ante tenfold.
Episode Eight: "Not So Holy Christmas Eve"
Following up on the previous episode's events, Igor and Margaret are suddenly back, Margaret congratulating Yu on his successful defeat of Izanami, then, as almost a Gut Punch, the original Persona 4: The Animation intro and music returns, emphasizing that Marie no longer exists.
During the ending theme, several parts are completely void of color with the scene where Marie turns around to see the Investigation team is replaced her turning to see absolutely nothing. The last part of the song, showing the memories that were made by Marie and the Team is completely black and gone, as opposed to Episode 2 where they were still lit up but blank white due to not being made yet.
Episode Nine: "A missing piece"
An in-universe example. The Investigation Team watches back some of the footage that was shot with their camera, but they realize that none of them shot the footage and none of them know who did. Of course, the viewers know Marie was behind the camera, but even then it is still very creepy.
At several points, they talk about things they did with or for Marie, and are confused and slightly frightened by the fact that they can't remember the person they're talking about.
Extra Episode
The OVA covers the Accomplice Ending from Golden. Only now we can better see Yu's reaction to hiding the truth from his friends and essentially selling his soul in a naive attempt to save Adachi. Even worse, the scream Yu gives out during all this and the despair in his face makes it look like he really doesn't want to go through all this but is being pushed to do so anyway, akin to fighting off a player railing him into a route he otherwise wouldn't take.
◊ ups the ante tenfold.
