Yumiko: I have t-ten people inside of me? B-but why is Yumie the only one who comes out?
Heinkel: Because that’s how we conditioned you. Every personality that Iscariot can’t use has been suppressed.
Yumie’s a berserker without morals. She’s a perfect assassin. But we don’t have the resources to supervise her all the time when she’s off duty. That’s where you come in.
You’re not the original personality, Yumiko. You’re just the only one old enough to take care of yourself, but not reckless or confident enough to ever think of running away. We’ve been using you too.