User blog comment:B214/Season 3 confirmed!!!!!!/@comment-71.13.210.73-20150111202639/@comment-213.122.115.99-20150215140005

If you want the key volumes for those U would need volume 8 the engaement ceremony(issei doesn't realise it but he is engaged to rias after this) volume 10/11/12 the confession the power of oppai and the revival and then I think some novel later where issei asks rias if he can talk to her casually in private times before they get discovered by sona