りゅうぐうのつかいであれば
竜宮の使いであれば
ryūgūno tsukaideareba

Noun
Da Copula

The "-eba" conditional form ("if/when…") of りゅうぐうのつかい

1. If/when a messenger of Ryugu Palace; If/when one is a messenger of Ryugu Palace

Ba Conditional
Usually Written in Kana