I don't know if I should have added the Chibi Miku tag, since there's two Mikus here.

Actualy this isnt chibi miku, it's petite miku due to the smaller miku having a pink color scheme rather than a white color scheme.
Tags changed.

I thought Petite Miku had a pink coloring scheme with her outfit. And the pixiv tags say ちびミク which is Chibi Miku if my limited knowledge of Japanese is correct. Petite Miku is usually tagged as ぷちミク.

I could be wrong though since I have no idea how reliable romaji.org is.

Check the pixv myself. It says chibi-miku. I'm going to change the tags.

cont from Tetsamaru comment:

Plus the shading on the little Miku's shirt is indeed white not pink. Also since she is based on Miku, she will pretty much have the same hair accessories.

Only Petite Miku has different accessories.

I have been having an idea that this was Chibi Miku and Puchi Miku... pixiv tags say Chibi Miku, Puchi Miku, Hatsune Miku and VOCALOID. Also, plus9 draws Normal Miku with grey shirt. Hair accessories don't matter.

I am quite sure that this is Chibi and Puchi Miku.

Then look at the tag on pixiv to confirm it.