This is an awesome game. Leveling your characters is very long and tedious but it helps a lot in the future events like boss fighting. I always choose Rena LOL cause I want to get Diaz, he is bad ass you know? To obtain certain characters you have to do something or involved in certain events. Unfortunately, you aren't able to obtain all the characters. Sacrifice are in order to get " certain characters " you like or want, accordingly to your own personal preference.