Having been trained as a cold-blooded assassin, Thirteen is first seen as a detached and cool-headed person but also prideful of her skills. When her mask is broken, it shows an easily flustered young woman who seems to have some trouble completely disregard her feelings of rights and wrongs. When Seven hits on her (which is during most of their interactions), she tends to act like a tsundere towards him. After a while she realized that she does love Seven anyways.

Prideful, tsundere, mostly cold.

Seven is goofy, a little absent-minded at times, and a bit of a pushover. He decided to become a killer supposedly because he lacks any morals and is only interested in becoming rich, but he never manages to kill his targets. This is partly because of his incompetence, but also because he actually doesn't want to actually kill others. His sense of justice slowly comes more and more into the spotlight after some time. Seven tends to be really naive and kind. He would never hurt his friends.