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.
History
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.
References To Mochitsuki In Existing Fangames
Mochitsuki's mat in Hallucigenia
A doll of Mochitsuki in Sick Mind
Gorotsuki is dressed like Mochitsuki in Dream Book
Gallery
Here are images of the most well-known characters of this fandom, with translated names. (Main source)