User blog comment:B214/Shin DxD 1 discussion/@comment-2607:FB90:3851:A5D3:0:14:ECCB:7501-20181029115052/@comment-2601:87:8300:20D0:5543:CD45:A7F7:DF0D-20181029210048

First I want to say thank you saying it clearer than what I said. It amazes me how he can figure out Vali and Grayfia, but not Rias. You can figure out sisters, rivals but not love or master servant relationships. To me it feels like he's not understand the relationship between between Rias and Issei. I thought it was obvious if you read the whole novel.

PS. How many times in the novel, anime and especially before they started dating Issei wanted to prove himself, to Rias and everyone else leading to the proposal for the future and beyond. Also you answered part of your own question when you said he joined because of his Rivals. Well news flash they've said a couple of times that there rivals even though there lovers.