Getting SR characters are not hard, and you can upgrade and unlock their true powers by just playing the game. I've been playing for 2 years. Unfortunately, I had to drop it because I can't keep up with new updates anymore. Having 5 teams maxed out and being unable to clear the new world, even with the right elements, is really a bad feeling. New raid bosses are impossible to beat. The new equipment system sucks because it completely disregards all the equipment you've previously put on your characters. All the other contents are ridicilously hard for no reason. The game gives you a sense of achievement and progression at first, but at later stages, it doesn't matter what your team comp is or how strong characters are because you'll never beat anything. The enemies are ridiculously strong they can kill you the moment the battle starts. I was having so much fun until I literally had nothing more to do to strengthen my characters and hit a wall I would never be able to break.