Shizuka Tatenashi/Plot

Chapter 1
While not explicitly featured in Chapter 1, she was one of the first people notified of Otonashi's actions.

Chapter 2
Shizuka was notified of Otonashi's return by a receptionist and coaxed him into her office to talk with him. When he made his attempt to resign, it was refused. She understood his situation, but made an attempt to convince him that his sister didn't want him to resign. This angered him and she let him go. Unknown to Otonashi, a person with glasses was observing him and seeing the failure of his immediate resignation, intervenes directly through unknown means.

Shizuka proceeds to call Otonashi's phone but he doesn't answer. In the voicemail she tells him that he's off the hook and to call her, clearly worried about his condition.