User blog comment:MiyamaSara/Have to do with the girl on Headmaster picture, Yume, Hime/@comment-26426093-20160814031116

You're the first person to officially post a blog regarding this subject on this wiki, you know? Thing is, I'm pretty sure everyone, including myself has all kinds of theories and assumptions about that mysterious girl in the photo frame. However, we only have one picture of her to go by, and to tell you the truth, she could by anybody at this moment, since we have so little information about her.

However, there are two facts that are certain: (i) she defintely must have been a member of the S4 in the past and (ii) she definitely has something to do with the main plot (the whole rainbow aura stuff).