Hatohara is a suspect wanted for the violation of key Border regulation by illegally providing Triggers to civilians and apparently have something to do with Rinji Amatori's disappearance. Because of her actions, she was officially fired and her unit was demoted to B-Rank.
Ninomiya mentions Hatohara when discussing Rinji's disappearance with Osamu and Chika. He notes the possibility that she could have been instigated by someone as she would not be able to come up with a plan as elaborate as the one they faced.
Later, while Chika is practicing sniping, Ema reveals that Hatohara was his mentor before her apparent dismissal. He mentions that she would never shoot a person. During this conversation, Chika accidentally reveals her similar mentality to Ema, and Yūma later suggests that Azuma and Ninomiya might have seen the similarities between the two, so they probably know as well.
After sniper training following her former team's battle with Tamakoma Second, Ema recalls how she deemed herself "useless" due to her inability to shoot people after Chika says the same thing. It motivates him to try and help Chika. Ema teaches Chika about Hatohara's idea of using Lead Bullet in conjunction with Lightning, something Hatohara could not accomplish due to her not having enough trion.