The Greatest Demon Lord Is Reborn as a Typical Nobody

The "school sword action" story revolves around Magic Knights, modern magic-users who fight with weapons converted from their souls. Ikki Kurogane goes to a school for these Magic Knights, but he is the "Failed Knight" or "Worst One" who is failing because he has no magical skills. However, one day, he is challenged to a duel by Stella, a foreign princess and the "Number One" student. In this duel, "the loser must be obedient for life." (Source: Anime News Network)

The second season of Mato Seihei no Slave.

The devilish haremking Issei Hyoudou is back for more outrageous Oppai Battle Entertainment in the scintillating second season of High School DxD! Fans who like their hardcore action spiked with a double dose of fan service won't be able to pry their eyes off all the scorching supernatural schoolgirls waiting for them in Season Two. So what are you waiting for? Plant yourself in front of the boob tube and watch a harem of devil hotties show you how much fun it is to be bad! (Source: FUNimation)

The third season of High School DxD. The Red Dragon Emperor, Issei Hyoudou, and the Occult Research Club are back in action as summer break comes for the students of Kuoh Academy. After their fight with Issei’s sworn enemy, Vali and the Chaos Brigade, it is clear just how inexperienced Rias Gremory's team is. As a result, she and Azazel lead the club on an intense training regime in the Underworld to prepare them for the challenges that lie ahead. While they slowly mature as a team, Issei will

Arata, Lilith and the rest of the Trinity Seven ace off against their greatest enemy; Lilith's own father, who is revealed to be the strongest Demon Lord. He challenges Arata who is now a Demon Lord candidate. (Source: Anime News Network)