User blog comment:B214/Volume 23 discussion blog/@comment-31.11.129.16-20170319160510/@comment-30924344-20170319231512

Bova doesn't need to be a Pawn at all if Roygun replaces him as Rook. All Issei has to do is before a match is say "Bova you are sitting this one out and Roygun will take your place for this match", hence why she is his substitute.