A chibi version of Vocaloid Hatsune Miku.
The supposed main character of the Chibi Miku-san 4koma by Minami. And is said to be the younger sister of the original Hatsune Miku.
She is usually energetic, hyperactive, and gets picked on by Kagamine Rin, who happens to be one of her guardians while the original Miku is away.
In the "Original Chibi Miku-san" arc (Chibi Miku-san #266 to Chibi Miku-san #298 ), chibi Miku is the original Hatsune Miku when she was younger.
This tag implicates hatsune_miku (learn more).