Man, your whole world with these characters in them just seems very appealing on its own. I wish you would expand a bit on daily life, other characters, etc. Oh, bios would be cool... But I'm assuming you've heard these suggestions before.
I'm conflicted between Umi and Chuubi D: they both are wonderful options? Why can't I have both! I think ultimately though I voted for Chuubi, not much beats getting fattened and snuggled, unless Umi were to follow it up!