User blog comment:B214/Talk About What You Want! 2/@comment-74.77.52.225-20140801025045/@comment-209.89.192.216-20140815163154

I never said it belongs to Issei, I said it would after he marries into the Gremory Family and becomes the head of the family and takes all of the responsibility that comes along with being the head of the Gremory family. Rias is the Heiress meaning Issei will become the head after their marriage. Issei isn't going to look after one small piece of land by himself but the Gremory lands with Rias and her peerage with the support of her parents from time to time once Issei becomes a HIGH-CLASS DEVIL.

Even if the land doesn't become Issei's, his responsibility as the head of the family won't change and he would need to look after the entire Gremory territory with Rias and the rest of the Gremory group.

As for the land you guys keep on talking about that he would need to maintain? did you guys forget? You first need to become an ULTIMATE-CLASS DEVIL before the underworld allows you to choose a land of your own. So Issei will recieve his evil pieces before he even gets a land that he needs to maintain.