Seina is first known simply as an old friend of Kanade, but is revealed later in the series to be a relative of hers. While Seina is of Jinguji blood, she did not inherit any powers, and as a result, had her last name changed. Near the end of the series, she is revealed to be the new chairman of V, a group that oversees the workings of the Jinguji family and controls even the family's leader (which was the main reason that Kanade had trouble rebelling against the family). This position was taken by Seina in an effort to help Kanade.
