Koyuki Miu (c) Skeyi / Wouda for design and voice respectively.
.ust (c) Mimirobo-P
I thought it sounded like a children's song, and thus Miu.
;3
"Hirahira" means "fluttering", by the way.
Voicebank download:
http://www.4shared.com/file/7fjD69hA/Koyuki_Miu_ACT1.html
More arts:
http://skeyi.deviantart.com