If you do a text search of the EoSD data files, you can find the name "冴月麟" (Satsuki Rin) near the other playable characters. Associated with her are the attack types 花符 (Flower Sign) and 風符 (Wind Sign). Some theories have been invented about this mysterious character, including that she is a Kirin (due to the matching character in her name) and that she is a nurse, based on a remark of Marisa's in the Extra Stage. There has even been fanart drawn of her.
