User blog comment:Raababukk/Possible New Power ups for Issei Hyoudou/@comment-23853100-20131014054544/@comment-9339850-20131015050327

you're right, since Issei's body is made of Great Red's flesh it allows them to fuse easily, though unlikely to happen again since that would mean Gread Red would have to leave the Dimensional Gap which he would probably never do