I appear to have hit a very large wall at rank 7 for Hikari...
Everyone hits a wall there. There are some of pieces that aren't farmable normally. Besides the "attribute orb" pieces being sold in the special shop in exchange for creation jewels (AKA the items you get when you get a duplicate stage girl in the gacha) these types of orbs can only be obtained in events and other various places besides normal grinding. I found this post on the subreddit that details these orbs and the various places you can find them.
In other words, no one, not even the biggest of whales, will be able to max rank more than a couple of stage girls for a while. So most players just consider getting to rank 7 at all "maxed out" for practical purposes, and only try to "fully max" their absolute favorite stage girls.
Having played Zelda recently, I will now refer to this as the Cloud Barrier.
Very well, I guess Hikari is all set now. Gonna work more on Tamao, Aruru, and Mahiru. ---
