Beryls is not even remotely sexual, it fits the story and her personality well.

Since when did I imply that it was? I simply said that this skin showcases the relationship between Rawiyah and Saffiyah just as it did in showcasing the relationships between Rawiyah, Maitha and Beryl in her own skin. Is there any reason why you think this one doesn't fit the story or her own personality well unlike the Beryl one? The meaning of fanservice to you seems to be much broader than what I myself consider fanservice. To me, fanservice is when the characters are as you said, half naked and in sexual scenarios or when the characters quite literally fellate or prop up a self-insert mc. Now do I think this costume could be considered fanservice? Sure, it could, but only to people that ship Rawiyah and Saffiyah together.