The name of the mystery character is likely Katja Böhm. I don't know how to create a character tag, nor an IP tag for 'Missing Stars'. It's a spiritual successor to Katawa Shoujo, taking place in a school for students with mental disabilities (I don't know what the PC term is). http://somnovastudios.blogspot.com/2012/03/character-preview-5-katja-bohm.html should give you some more information. I expect to see more Missing Stars / Katawa Shoujo crossovers in the future.
EDIT: Figured out how to make copyright and new character tags. Appropriate tags added, remove if I did so in error.
