Was good, but increased monetising of late makes it much less enjoyable
First “skips” on long winded battles were taken out unless you are a high level VIP (needing spend to reach), then various daily challenges were made harder and harder (not just from levelling - one day you could complete a whole battle series fairly easily, then after update even the first battle in a series of 10 or 20 you couldn’t win). Rewards started being changed and reduced. Bugs started appearing from the frequent updates to add more monetisation and make the game harder and harder and to slow down progress. Then the daily gold coins used to buy items or progress characters or even perform certain daily quest/activities in game, although limited before, suddenly stopped, completely. New levels and content also slowed down being added and it may be, like many games, the difficulty and cost was ramped up as people were burning through content too quickly which was costing the developer too much to create.
So as a free play game it was originally good, especially if you liked the anime, but now increasingly heading towards a grindfest heavily-monetised game, sadly.