You will be able to increase even more the Stats of your characters by assigning them new items, available by making an expenditure in the event swiftness release (Partner or Akatsuki) and Six Paths style (Fate or Kaguya).
I) Partner
Each improvement will bring you an increase in HP, ATK, DEF, Crit, Res
II) Akatsuki
Each improvement will bring you an increase in HP, ATK, DEF, DMG increase, DMG decrease
III) Fate
Each improvement will bring you an increase in HP, ATK, DEF, Super Crit, Super Anti-Crit
IV) Kaguya
Each improvement will bring you an increase in HP, ATK, DEF, Super Crit, Super Anti-Crit