The casino is my favorite place here, or rather, playing poker. I would probably spend the whole day here if the side story event wasn't pressing. So far, I've gotten 900k chips (I spent some on anime and elixirs just to have them), but I think 5 million is not far off.
Added 24 minutes later
I can't... Stop...
I got 2 million and now I have the opportunity to unlock a specific character, but it's quite expensive. By the way, I hate level 8.