Azuma Tokaku is a distant and cold girl. Even at first glance, she has the appearance of an assassin. Azuma dislikes it when other people try to get close to her, and she especially hates being called by her first name, but Haru compromises and calls her "Tokaku-san." She is skilled with using knives, and has exceptionally quick reflexes.

During Inukai Isuke's attack on Haru, it is revealed that Azuma has never killed anyone before, despite possessing very useful skills as an assassin. After the attack, Azuma vows to protect Haru from everyone else, making it 11 assassins versus one target and one guardian.