Ummmm....After taking a really long look at your sketch I can see few things that you REALLY need to improve in original
designs
1. Don't make noses too much "pointy", they look really weird in that way, try to make noses small and
curvy, so they'll look like "anime/manga style".
2. Necks of the characters are really long, they are not swans, and try to make the necks according to the physique of
characters i.e. muscular characters should have wide neck and slim and skinny characters have slim cute neck.
3. Clothes! they should have more folds and when you color them clothes should have more "textures" to make
them look more appealing (I also have to learn to give textures in clothes XD)
4. Hairs are too simple, I am not saying hairs are looking bad but still you need to make hair much more better like
your doujinshis (in your doujinshis you make hair so good) so try to make hairs in various different styles, there are
pretty lot of hair designing ways in anime/manga which are common and easy, try drawing different styles and stick with
the style you like most!
And the part that is making your sketch looks weird is the mouth of guy, it's looking out of place, when we listening music out mouth is either singing or have smile, not a weird expression.
And The things that I like most are legs! and shoes! they're looking so good!