OriYume (オリ夢)

Overview
OriYume (オリ夢, Original Dream) is a Japanese Pixiv fandom created by Yume Nikki derivation fans who wished to create their own Yume Nikki fangame. These were games under construction which created a wide list of possible characters that could be in them. As a result, no games were produced, and the characters were left as a concept art. The source of it's name is "Original Character(s)", オリキャラ, which explains the large number of characters this fandom produced.

The Most Well-Known Characters
Here is a list of the most notorious OriYume characters with their original creator's concept art and sprites.

Mochitsuki
Mochitsuki (もちつき) is a grey-haired girl with bunny ears with a beauty mark in a yellow tank top over a black dress. She is highly referenced in already existing fangames, some of them are even more famous than the fandom itself. Mochitsuki is often depicted with a Mochi hammer, which might be a prototype of her weapon effect.

Gallery
Here are images of the most well-known characters of this fandom, with translated names. (Main source)

External Links / Further Info
Pixiv Encyclopedia Page

Pixiv Art Tag