Save file help

Okay so, I originally played DT when it came out like literally in 2018 so I had an incomplete chapter 1 save file when I downloaded the “full” game this month to play up through chapter 5.

I guess I started in save file 2 and then ended up deleting my original demo save file, and saved the rest of my progress into the first save file slot.

Now, on the chapter 1 first save file slot I beat Jevil and got his knife and shadow crystal which I obviously want to hold onto. Do I need to delete my already existing chapter 2 save file? Obviously when I tried to load it, it just chapter selected to my recent play through’s castle town and I’m kind of scared to do anything lest I lose my shadow crystal or my other play through.

If anyone has any advice, please share. This is such a dumb predicament I got myself into.