I liked your opening where you started off by describing a death body. This has created a nice hook to the story.

I can see how Cory loved his sister through his memories/flashbacks of her. Ari is also a very interesting character who has an unique chemistry with Cory is capable of comforting him in his struggle of loss and pain.

The overall story plot is clear, but I think you can consider reworking some of the relatively long sentences, which I find it a bit hard to dissect and read sometimes:)