Hatsune Otonashi/Plot

Events prior to A Step Closer
Upon Otonashi's revival, Hatsune remained alive even past her original death date on Christmas. Otonashi, still inspired by her and the events of Angel Beats, continued with his medical studies and was able to become a doctor of cardiology. However, despite Hatsune's continued observation and treatment in the hospital, her condition continued to deteriorate even after being given priority and more advanced treatments.

Prior to her finals moments, she signed a Do Not Resucitate order and acknowledged to her doctors that she voluntarily gives up treatment, unknown to Otonashi. One visit to her, he notices the DNR notice and in an upset rage, hides it, wanting to buy more time to treat her.

Events of A Step Closer
Following Otonashi's removal of her DNR notice, she finally codes and doctors come in to resucitate her but someone who knew about the DNR notice it was missing, causing an argument amongst the emergency team.

She's officially declared deceased and Otonashi, who was last seen in the room, is accused of medical malpractice which ultimately leads up to the events of Angel Beats! A Step Closer.