with regards to their personalities, show, don't tell. a comic is good, and ok, maybe you drop a wikia page on how you envision them, but in the end, it's the songs they sing that will really convey their personalities. these are voicebanks first, characters second (traditionally).
obviously, do what you want with your own original characters. there's no harm in making a character based off your UTAU and making it more than just an UTAU. but i'm going under the assumption that these are UTAU and that that's all they'll be taken for. rin, len, kaito, miku-- the vocaloid characters come with very little characterization. you've got the quality of their voices to go off, and the design of the characters, and those are interpreted (or ignored) through song. kaito is not packaged with the yearning and desire to be human and feel love, with the heartbreak of fearing, ironically, that he'll never know true emotion. the nuance in their characters are expressed and interpreted through the songs they're made to sing.
so obviously the solution is to get out there and write some songs for your UTAU that really demonstrate their characters. but alas, utaites at large only publish covers of other people's songs.
and then there's weird ones like Alice Human Sacrifice or Bacterial Contamination, which are really more about a concept or that characterize the producer more than the character.
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i think the voice quality of your pair is probably fine. i naturally don't much like yuki because you used a slow song for her, which makes me think she'll be more suited toward ballads and it will be difficult to use her in more energetic songs.
imo drop the hoodie concept and go with something else. it's fine to have hoodies, to use hoodies, but don't make it their default. we all have that stage (i'm actually wearing a hoodie right now), but it's not professional, it makes you look like a teen slacker, and it's not cool unless you're like, a rapper or something. it's not the flavor you're going for.
unless there is something specific you're going for, model your characters after pre-existing, japanese, yamaha vocaloids. i'm not telling you to copy the design completely, or even in-part, i'm just saying make something that would fit aesthetically in the Miku Miku Ni Shiteageru music video.
miku hatsune, for instance, has a pretty bold design, despite the muted colors of her outfit. i'm not referring to her hair, either, i mean she has bold, solid colors, and clothes that break those colors up and spread them out. did you know her sleeves aren't attached to anything? just black sleeves that start above the elbow, with the aqua trim. the sleeves connect to the arms, which connect to the vest, which connect to the skirt, which has some trim as well to separate it from the stockings. there's also a bit of Absolute Territory there, but the trim is required for the skirt to match the sleeves, as well as to help separate the black skirt from the black stockings. while it looks fine, it's pretty impractical to have sleeves that don't attach to anything, wouldn't you say? plus the outrageous hair. plus such a short skirt (maybe). but it's perfect for a virtual idol-- the flavor of yamaha's vocaloids.
i'm rambling again. but it might do you some good to start with a high concept of what "kind" of characters yuuki and yuki are. if they aren't pop idols like rin and len and the crew, what are they? if you're going for a more pedestrian flavor, your art makes yuki look like a college student. from her "personality" given and her current design, she strikes me as the sort of girl to be pretty popular and fun, and even if she is insecure, probably has had a lot of boyfriends and is easily flattered. yuuki, though, seems like the type to never make a move-- if they're supposed to be a romantic couple, one of them has to be able to approach the other.
[doublepost=1467937484][/doublepost]i actually wanted to mention something about "mary sues," too.
just because the characters have some aspects of your personality, that doesn't make them bad characters. i believe that's pretty normal of any character we're supposed to like or sympathize with. it would be more of a problem to make a character that had none of your characteristics.
you might go one further and make caricatures of these aspects you possess, because that's an easy way to make a strong character. and since you're working with voicebanks, who will largely be determined by what songs they cover, starting with a strong, simple profile could go a long way.
(still, you need to make sure the voices actually do match the characters. if you make a high-octane shoujo character who has a deep alto voice that's only suitable for sad, slow, operatic pieces, people will take your character and change it.)
inb4 mods merge my posts
