Issei Hyodo is your average perverted high school student whose one wish in life is to have his own harem, but he's got to be one of the unluckiest guys around. He goes on his first date with a girl only to get brutally attacked and killed when it turns out the girl is really a vicious fallen angel. To top it all off, he's later reincarnated as a devil by his gorgeous senpai who tells him that she is also a devil and now his master! One thing's for sure, his peaceful days are over. In a battle between devils and angels, who will win?

[Source: FUNimation]

A series of 3-5 minute specials that were bundled with the HighSchool DxD DVD and Blu-rays. They are a stand alone set of episodes that are not a part of any story line in particular.

Special 1: Going Sunbathing! - The Occult Research Club goes on a beach outing.

Special 2: Issei's Private Training! - Issei is being given lessons in magic by Akeno.

Special 3: A Little Bold, Koneko-Chan... Nyan! - Koneko accidentally has her personality reversed magically, making her incredibly sexually active and reversing her sexual preference.

Special 4: The Untold Story of The Dress Break's Birth! - A few flashbacks of how Issei first found out and eventually perfected his special move, Dress Break.

Special 5: Making Udon! - As part of a penalty for losing a bet, Sona and Tsubaki make udon for the Occult Research Club but the udon comes to life in a peculiar way...

Special 6: Asia Transforms! - Asia wants to prove she is just as bad as any demon by using ideas found in Issei's magazines, going as far as dressing up like a harlot and seducing him.

[Source: Wikipedia]

#1: Oppai, Minorimasu! (Episode 13)
A rumor is going about the school about how girls are disappearing and coming back ill and with their breast size decreased.

#2: Oppai, Motomemasu! (Episode 14)
While observing how the others do their jobs so they can do theirs better, Issei and Asia go with Rias to see if a coffin is cursed. During the investigation Issei is possessed by an Egyptian magician named Unas, It just so happens that Unas is just as perverted as Issei. Unas will only leave Issei's body if they can release Unas from the curse placed on him by a devil that Unas tried to make his bride.

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]

Asia is attacked by a monster which stole her undergarments as the Occult Research Club arrives to rescue her. Facing trouble to fight that monster due to Asia's request, they managed to destroy that monster with the help of the timely arrival of Irina. Rias then receives a message from Yuuto telling them that Gasper has found the source of the magic. As they arrive to the source of the magic, the Occult Research Club and Irina decides to split into two groups with Akeno and Asia staying behind. The advanced group then encounters the individual responsible for the monsters as he reveals his past story with Issei being in awed with him. Azazel suddenly appears and reveal that the priest who has been stealing women undergarments is the man closest to achieving the Philosopher Stone. Preparing for another spell, the priest halted half way due to the lack of perversion as Koneko reveals Gasper's panties causing the spell to go wrong as the priest became an underwear monster. The underwear monster starts to gain advantage by stripping the girls and manipulating their bras. After having the girls surrounding Ise, the underwear monster, now jealous decides to absorb the girls instead. Issei having determine that the priest is mistaken starts a preach about breasts causing the underwear monster to be in doubt. With Azazel's advice, Issei defeats the underwear monster using Dress Break and the priest is captured. Before leaving, the priest leaves the stolen undergarments to Issei, as Rias and the others decides to leave returning the undergarments to Issei.

[Source: Wikipedia]

The babes and boys of the Occult Research Club are Back! Lovable loser (and bust buff) Issei and his clan of bewitching beauties return for a new season of supernatural tussles and sexy shenanigans—featuring old friends and new enemies! Now that all the girls live in Issei’s home, life seems like nothing but fun and scantily-clad lounging…for now! Join Rias, Akeno, Koneko, Asia, Xenovia, Gasper, and everyone’s favorite Harem King Issei as they fight, fumble, and fondle their way through their demonic high school lives.

[Source: Funimation]

Specials included with the Blu-ray/DVD volumes.

Unaired anime episode bundled the limited edition High School D×D DX.2 light novel.

Adaptation of the second half of the Heroic Oppai Dragon arc of the original light novels.