User blog comment:B214/Volume 23 discussion blog/@comment-26821288-20170205085556/@comment-31137559-20170208024629

He did that most likely for the reason for having Issei confess to Asia, Xenovia, and Irina all at once. He would be alright with Asia being ahead of Akeno. But having Issei confess to Irina and Xenovia before Akeno would put her behind them and he didn't like that. So he had her be the second girl he confessed to. And Asia's place is kind of already established. The care Issei and Asia have for each other is clearly established between them. Some people will persist with "Issei sees Asia as a little sister!" although that hasn't been the case. They look more like a loving couple than brother and sister. And Issei could have known since he confessed to Rias how the other girls feel about him. And he has been trying to sort out how he sees them. And plus with all the stuff going on he never found the right time because if he confessed to them he would just have way more to deal with. And with him wanting peace, he has mentally blocked himself somewhat from having a harem. Now with the stuff with Trihexa over with and them finally having a break, Issei has found the perfect time to confess to the girls. We already saw how Issei and Rias had a hard time getting time to themselves. So having any more of that wouldn't do. He just wanted to find the perfect time when his schedule isn't all packed with all the shit going on so he could give them the necessary care and attention and work on becoming harem king.