Thread:Staraptor Kwan/@comment-15568664-20161017003105/@comment-26426093-20161116123510

There has been plenty of discussion regarding her identity on this wiki and elsewhere, but a common theory is that she might be related to Hikaru by blood (sister/cousin). It's also possible that she could have been his lover in the past.

One thing is for sure: Hotaru (that's her name) must be an adult by now: back in Episode 27 when Yume and co were leafing though an old yearbook containing a list of former S4 members, it was mentioned by them that Hotaru was the first ever S4 member. And when you take Hikaru's estimated age into account, that seems to become less and less of an coincidence.