Omgggggg!! Your drawing looks extremely good! I like your drawing style so muchhh!! It's amazing and so unique! You didn't mess up anything, he looks really perfect and I appreciate the fact that you noticed his ring and small details ^^!! Thank you so much for taking your time and draw him !!!
As for the voice, I haven't decided yet ,I like to let the players decide and imagine Luno's voice, because everyone has their own idea of him :3 For me the most similar voice to Luno's, I think would be Nagito from danganronpa but more softer maybe
Also, Keep it up! You are an incredible artist and I like your art so much!^^