Yes, you have to buy the uniform from Kotomine and give it to Sakura to get the CCC sequence/ending and fight Kiara, among other flags you have to trigger that I don't remember (nothing that makes you go out of your way, IIRC). This'll result in Sakura's ending (CCC). Servant endings occurs when you bond with your servant and don't get the CCC flags, or you do get the flags but make a choice at the endgame that locks you out. Same goes for the normal ending, except you don't bond with your servants. Kiara jobs to Melt in the normal and servant endings and BB is the final boss.