User blog comment:B214/General Discussion/@comment-27083298-20161027142216/@comment-27083298-20161027151252

Without Issei the girls could not resolve the issues they had.

1. Rias would've been stuck as Riser's fiancé.

2. Akeno would continue to be traumatized and never resolved the issues with Baraqiel.

3. Raynare can completely kill Asia or be taken by Diodora.

4. Koneko would continue to be in fear of her Senjutsu powers