Well, the art's lovely and the actors are quite good, but honestly, the writing needs serious work. The biggest problem to me at this point is characterization.
Sam states repeatedly that he's not worthy of his brother's love and protection, or of Cyrus's friendship. But why does he feel this way? He doesn't seem to have especially low self-esteem. For that reason, his constant self-deprecation sounds rather hollow.
The Kaitos twins bored me. So far they're just your everyday school bullies. They're supposed to be geniuses or something, but they didn't get a chance to do anything but be awful to Sam. I understand that that might be your intention for this portion, though.
Your second biggest problem is tense: pick one and stick with it.
Thirdly, don't abuse letters or punctuation. This may have happened because you wrote the dialogue so that the voice talent could best understand the emotions needed in each line, but generally speaking, you don't need every emphasized word to be in all caps or stretched out like thiiiiiiis. A skilled actor (and reader) will be able to determine a character's tone of voice and intent if the writing is strong. And use interrobangs sparingly. I'm begging you.
You can see my full list of suggestions via the link below. (Note: I decided to go with present tense since that dominated the majority of the script, but you may want to choose differently.)
https://docs.google.com/document/d/1CEJ ... jHdiM/edit