User blog comment:B214/Volume 21 info & spoilers/@comment-24.113.129.70-20160416024525/@comment-27876048-20160420105342

@anon you have to keep in mind that it has only been about a year since issei has started to come into his own we all will see him get wayyy stronger in future volumes, especially if the author decides to make a sequel series that takes place after the events of highschool dxd.