>>534055740
No once a doll goes on its stuck.
If it's a R level doll (the crapper ones) it can be ripped and replaced with an SR (the better one) for free and you keep the points you put into it.
You should probably just save up your blue dolls so you can trade them in for doll kits.
Getting a SR doll to level 15 can take a shit load of doll kits.
It's possible to do it in 3, as every kit has a tiny % chance to jump 5 levels at once on use (but statistically it's almost certainly not going to happen).
I think one time only I finished a doll off in a single day from 0 to 15. I just got very lucky with the kits.
Some select character can go to SSR items (the gold level). Where your level 15 SR doll can be transformed into a unique item. These require you to have a bond 30 and do a little side quest (these are always easy but the story is pretty good). The cool thing about the unique items is they give you a really nice flashy menu reskin and they unlock a bunch of abilities that are so good they'll instantly push your unique item Nikke'a to the top of your roster in terms of battle power.
Some are more broken than others but they're all pretty fuckin good.
Once you get a unique item the real grinding begins.
I'm currently feeding Viper 110 phone chargers, that I painfully slowly acquire 1 or 2 every week or so.
The solo raids give you shit loads and there's mechanics to swap them 5 to 1 once you max an item out.
Welcome to the grindiest part of the whole game lol.
I dunno maybe the cubes are grindier. I've got like 3 unique items maxed out but not a single cube yet.