High School DxD is one of the most popular ecchi action series out there, but despite just how popular the anime has been in the United States it's not possible to legally look up the original source material as the light novel series the anime is based off of does not have an official English language release. Although the original series now has 25 volumes under its belt in Japan, and even began an official sequel last year, there's still no sign of them in the United States. Unfortunately the producer behind the anime series, Satoshi Motonaga, has no answer there either.
Speaking with Monsters and Critics, who asked Motonaga whether or not there were plans to officially release the original light novel series in English officially, Motonaga revealed that he could not speak on the matter. While it's not a no completely, Motonaga revealed that it's a hard question to answer.
As Motonaga explained, "That’s a hard one to answer. There are some conversations but they haven’t really matured into anything. It’s hard to answer." So while the anime could potentially have a future adapting more materials from the original source, those in the United States will unfortunately be left in the dark for future events. That'll be a much different ballpark for many anime watchers, for sure.
But Motonaga does have an eye on the United States market as the anime has done pretty well in the West, The anime has also done well outside of Japan, especially with the new season of the series, "Our impression is certainly that this title is a very strong title outside of Japan. I think the sexy [ecchi] genre is kind of shrinking in the Japanese market. Not that we are specifically making this for the foreign market, it just naturally seems to resonate really well. There’s always going to be a core fanbase but sales-wise I think it’s safe to say the Western markets are becoming a lot stronger in terms of this type of content."
Originally conceived as a light novel series written by Ichiei Ishibumi with illustrations by Miyama-Zero for Fujimi Shobo's Dragon Magazine in 2008, High School DxD follows a boy named Issei Hyodo who is best known for his perverted ways. After being asked on a date, the boy is killed when the girl turns out to be a fallen angel. Issei is revived by a busty classmate of his named Rias who is a devil herself, and she contracts the boy to become her new pet as she reincarnated him into a devil during his resurrection. The series is currently four seasons total, and the full run can be found streaming on Crunchyroll and FunimationNOW.