But as noted, the Rainbow Crystals are an anime only filler arc.
Actually, there's another option. IIRC Canonically Beryl was chasing after the Ginzuisho in the manga and anime, or at least it was one of the targets she had. It's possible that she'd detected it was in the general vicinity of Azabu Juuban and focused her efforts there because she wanted to look for it anyway. A long term energy gathering operation can easily be turned into support for an information gathering operation. The biggest issue is having people around in the first place.
Actually, there's another option. IIRC Canonically Beryl was chasing after the Ginzuisho in the manga and anime, or at least it was one of the targets she had. It's possible that she'd detected it was in the general vicinity of Azabu Juuban and focused her efforts there because she wanted to look for it anyway. A long term energy gathering operation can easily be turned into support for an information gathering operation. The biggest issue is having people around in the first place.