A nice peaceful song! It'd probably go well as background music for a cutscene, but if I were to judge it as music to listen to by itself, I would say that it needs to have more of a memorable high point somewhere, or a memorable melody or riff - that's generally what keeps people coming back to a song, or at least that's what will keep me coming back. Again, since this is meant to be a theme song for a character, it would be very useful to have something unique that audience members will remember and mentally connect to that character. For instance, if I were to play Megalovania out of the blue, you would instantly think of Sans. I can gather resources for you if you want to bolster your melody-writing skills - I know where to find them. :)

Sounds cool. The strings are a little bit cheap, try to teak the ADSR enveloppe if your plug-in allows. It has some mixing issues but nothing serious. Be careful the synth at 1:04 is really loud.
Really cool job, well done,

~ Ahurac