User blog comment:TheBlueSlug/Ending/@comment-213.120.234.122-20141115123857/@comment-1359322-20141115233740

Actually it's not that Issei doesn't want just Rias, Issei is currently focusing on Rias only since they are lovers. It's the girls that doesn't want to give up. Issei himself isn't that determined to take on other girls aside from Rias yet.