At episoode 9, Otonoshi did not died in the train accident, he survive and help the other survivors with his knowledge in medicine, but there were trap and there only 3 days worth of food and water, the survivors despair about there doom but Otonoshi give them hope to live because that what his little sister thought him when she still live. For 7 day they were about to died, Otonoshi bring out his organ donation card and his name for that even his dead, his body can be use to help others to live, and the others do the same that even at the brink of death there still a purpose to live. At the same time the close tunnel were open by the rescue party but at that time Otonoshi have died from internal bleed before there were rescue.
After remembering all, he suppose too disappear from no regret but he didn't because he still think of his friends, so Otonoshi and Kanade need to work together to bring the same satisfaction that he have to the SSS.
What a wonder story that really make me cry, Jun Maeda sure know how to bring emotion out of this story.