The characters blend into the background. Since you have white and that very dark grey in your palette, it might be a good idea to use a bit of those on the characters to make them pop.
At first I culdn't find the main character because between the vaguely triangular silhouette and the low contrast, all the characters looked the same to me. Since you can't use colour to establish distinct visual identities for each sprite, you have to make particularly good use of silhouette and value to do it.
eishiya / Thank you for advice! It's very helpful to me.