Gakuon Yuki is a Fanmade Vocaloid/ Pitchloid create and illustrate by Celine Ruo Ting Tey.
(Gakuon) means Happy Sound or Cheerful Sound.The kanji Gaku means Happy or Cheerful, On means Sound.
(Yuki) means Snow.
Put them together and it means "Happy Sound of Snow" or Cheerful Sound of Snow". Her name is create by the creator of Kotone Senmi.
Gakuon Yuki is based on Hatsune Miku or Teto Kasane's appearance.Her two pony tails is short like Teto's (not Drill).
Just like her name. She is cheerful and kind-hearted.Sometimes she get bullied by Kotone Senmi.
She is born on Winter (date unknown). So, her name is Yuki. And her past is unknown.
Her voice is lower pitch than Hatsune MIku.
Gakuon Yuki & Kotone Senmi - Matryoshka 
- Her name also can called "Gakune Yuki"