Quote Originally Posted by Yil at himeuta
Some details on rarity upgrade I gleaned from elsewhere:
1) You get "rarity upgrade material" from rolling premium gacha and danchou medals exchange.
2) Raising unit's skill level and releasing equipment slots decreases amount of "rarity upgrade material" needed for this unit.
3) Players will get "rarity upgrade material" for all their rolls since december of last year
4) This thing is getting released in march
5) It will be available only for specific units, like blossoming. First batch will include winners of current voting contest (first place of each rarity, first place of each country)
Lower rarity girls will be upgradable to rainbow, but what will they gain? Surely they won't be equal to 4-slot gacha rainbows.