User blog comment:B214/Question and Answers 3/@comment-4547267-20140704165314/@comment-1359322-20140705030320

The only one that considered suicide is Asia, but she couldn't do it because she knew that Issei would be angry at her. Rias and Akeno just lost their will to live entirely, they were like dead souls in a living body.

Well it's understandable why neither Rias and Akeno could commit suicide though. Both of them carry heavy responsibilities with them. Rias still has her duties as the heiress of the Gremory. Plus after losing the center of the team which is Issei, if either Rias or Akeno commit suicide, the other members would just follow pursuit, this is like killing their friends with their own hands. Supposing if they don't commit suicide, Rias' servants would lose their master, and no one knows what will happen to them. So Rias and Akeno have their hands practically tied in a way where they don't want to live, but they can't end their lives.