What is rarity growth, anyway? Doesn't seem to be introduced yet with Nutaku.

EDIT: Ah, okay. So I'd want to bloom Ardisia Bride into her bloomed form and max her levels, but not use any skillblooms or dressblooms on her until after rarity growing her.

Bummer. I already used dress and skill items to max out the 5* characters I'd most want to rarity grow.