Below may include Non-Canonical info
Hype-Chan is a fan-given name to an unnamed character that appears at the end of Solo Remix.
She appears to be a mixture of all of the main characters; Her red skirt and white button-up shirt she wears reminiscences Beat (his white tank top with a red one under it); she has headphones like Neku Sakuraba; she has a plush alike to Shiki's Mr. Mew; her eyes and posture are similar to Rhyme. Her hair color reminds of Joshua.
While considered as the "Proof of A TWEWY Sequel", not much has been said about this "character". She's seen after watching the Secret Ending (you will get the "A New Shibuya" Achievement after leaving the Game's Photo).