くろとうぞくかもめであれば
黒盗賊鴎であれば
kurotōzokukamomedeareba

Noun
Da Copula

The "-eba" conditional form ("if/when…") of くろとうぞくかもめ

1. If it were a black thief gull…; If the black thief gull existed…

Ba Conditional
Usually Written in Kana