Albion: We are conflicting existences. To do that would be suicide.
Ddraig: So you know, Albion, possessing this master has taught me something important. Even a fool can make the impossible possible, as long as he never gives up!
The third story arc of Highschool DXD, which comprises Volume 4 of the light novels, Episodes 7-12 of the anime's second season, and Volumes 7 and 8 of the manga.Ddraig: So you know, Albion, possessing this master has taught me something important. Even a fool can make the impossible possible, as long as he never gives up!
— Albion and Ddraig as Issei attempts to fuse the former's power with the latter.
This volume provides examples of:
- All for Nothing: Katerea Leviathan worked for several years to cause chaos in the Underworld and plots to break up the peace treaty between the Three Factions and kill both Sirzechs and Serafall, two of the Four Great Satans she deeply resents. It gets undone when Azazel fights and kills Katerea by running his light spear through her, allowing the Peace Conference to be completed without interference.
- All Your Base Are Belong to Us: Katerea leads the assault on Kuoh Academy during the peace conference. Her plans get foiled in an awesome way.
- And This Is for...: During Issei's first fight with Vali in the finale of Volume 4, Issei becomes enraged when Azazel makes him think that Vali intends to use his dividing powers to reduce the girls' bust sizes. Issei hammers Vali, all for the sake of protecting the girls' breasts.Issei: This is for Rias and her mammoth love melons! (punches Vali) And this is for Akeno's huge honkers! (headbutts him) This is to make sure Asia gets to keep on growing! (knees him) For Xenovia's killer gazongas! (punches him again) And this is for Koneko's poor itty bitty titties! You can't divide them! The only things left would be very lonely nipples! (punches him yet again)
- And Your Little Dog, Too!: Issei attacks Vali when he threatens to harm his family and Azazel makes a notion that his Half-Dimension will halve the size of his harem's breasts.
- Back for the Finale: Zeoticus, Sirzechs and Grayfia, and Irina return for the finale of New, which is adapted from this volume.
- Big Bad: Katerea is the main antagonist of the volume as a leader of the Khaos Brigade's Old Satan Faction. She's willing to attack the peace conference to carry on her faction's ideals.
- Big Badass Battle Sequence: The alliance between the Angels, Fallen Angels and Devils vs. the Khaos Brigade at Kuoh Academy.
- Bittersweet Ending: The Peace Conference is successful and the Angels, Fallen Angels and Devils settle their differences; Katerea is dead and the Khaos Brigade's invasion of Kuoh Academy has been thwarted; Michael forgives Xenovia and Asia; and Azazel becomes the Occult Research Club's advisor. However, Vali escapes and plans to fight Issei again in the future, and worst of all, the Khaos Brigade is still out there.
- Bullying a Dragon: Vali knows how dangerous Issei is, but that doesn't stop him from taunting Issei about how he's going to threaten his family before his Curb-Stomp Battle.
- Dawn of an Era: The Peace Conference marks a new era for the Devils, Fallen Angels and Angels after many years of in-fighting.
- Early-Bird Cameo: In the Blu-ray release of the anime's second season, Ophis appears in a brief cameo.
- Earn Your Happy Ending: By the end of this volume, Angels, Fallen Angels and Devils held a successful peace conference and end up forming The Alliance, ushering in a new era of peace.
- Easily Forgiven: Even after Asia and Xenovia have learned the truth about God, Michael forgives them to the point that they are allowed to pray for them.
- Foreshadowing: Throughout much of the volume, Akeno refuses to acknowledge her relation to Baraqiel. Guess what she says to Baraqiel when they first meet in Volume 7?
- Gone Horribly Right: Played for Laughs with Vali's plan to make Issei fight as hard as he can by taunting him about how he's going to kill his family, even using Half Dimension to halve his harem's breasts. What happened next is pretty much foregone.
- Greater-Scope Villain: While Katerea serves as one of the leaders of the Old Satan Faction, the Khaos Brigade proper remains Out of Focus for this volume.
- Half-Human Hybrid: Akeno reveals herself as a Fallen Angel and Devil hybrid to Issei.
- Heroes Gone Fishing: After Kokabiel's defeat, the Occult Research Club goes out to the academy's pool and clean it before they go swimming.
- Hoist by Their Own Petard:
- Katerea Leviathan, a leader of the Old Satan Faction, spent years planning to cause chaos for the universe. As part of her plans, she assaults Kuoh Academy to break up the peace treaty between the Angels, Fallen Angels and Devils. This instead prompts the Three Factions to fight Katerea's forces, leading to her own demise.
- Played for Laughs during Vali and Issei's first battle. Vali taunts Issei that he will kill his family, which triggers Issei's Big Brother Instinct and unleashes his Unstoppable Rage to easily overpower Vali.
- Impaled with Extreme Prejudice: The fate of Katerea Leviathan at the hands of Azazel's light spear.
- Minor Crime Reveals Major Plot: The attack on the Peace Conference reveals the existence of the Khaos Brigade.
- Nice Job Fixing It, Villain: Katerea and her mooks attacking the Peace Conference was meant to break up The Alliance; instead, it lead to a massive boost for the alliance to negotiate a peace treaty. Not only that, but she singlehandedly caused Azazel to kill her before resigning as the Fallen Angel Governor to become the Occult Research Club's adviser.
- Non-Protagonist Resolver: At the end of this volume, Katerea Leviathan isn't killed by any of the main protagonists; that honor belongs to Azazel.
- Nothing Is the Same Anymore: For the first three volumes, the Angels, Fallen Angels and Devils are fighting amongst themselves. By the end of this volume, the Peace Conference ensures that the Three Factions will end their hostilities.
- Oh, Crap!: Katerea has a moment of utter shock when Azazel hacks off his arm and is about to kill her.
- Peace Conference: Azazel seeks to negotiate with the Three Factions to bring about a peace treaty. It succeeds.
- Post-Climax Confrontation: Katerea is killed and the Khaos Brigade is forced to retreat. However, Vali turns on Azazel and decides to fight Issei again.
- Pre-Mortem One-Liner: Before killing Katerea with his light spear, Azazel says "An arm's nothing."
- Rage Quit: Once Azazel out-matches her in combat, Katerea decides to just blow herself up and take him down with her. It doesn't work as Azazel ends up killing her.
- Relative Button: Vali threatening to kill Issei's family and cutting down half of his harem's breasts immediately cause Issei to overpower him in their battle.
- Re-Cut: The DVD and Blu-ray release notably adds scenes involving Ophis.
- Shut Up, Hannibal!: At the conclusion of their duel, Katerea tries blowing herself up in a bid to take Azazel down with her. Azazel responds by cutting off his arm and throwing his light spear at Katerea, which leads to her Disappears into Light death.
- Skewed Priorities: When Azazel reveals his true identity to Issei, instead of being pissed for his subordinate Raynare killed him and Asia, he's angry at how Vali's intervention prevented him from sucking Rias's breasts.
- So Long, Suckers!: After his No-Holds-Barred Beatdown at the hands of Issei in volume 4, Vali tells Issei that they will fight each other again.
- Those Wacky Nazis: The Khaos Brigade.
- Undying Loyalty: Even as Akeno reveals her Half-Human Hybrid heritage to Issei, he refuses to abandon her.
- Unstoppable Rage: During their battle, Vali threatens to kill Issei's family and Azazel states that his dividing powers will reduce the girls' bust sizes. This sends Issei past his Rage Breaking Point and he delivers a No-Holds-Barred Beatdown on Vali.
- Unwitting Instigator of Doom:
- Azazel sending Baraqiel out on a mission unintentionally causes Shuri Himejima's death when her daughter Akeno was a child, causing a huge conflict between the latter and Baraqiel.
- An inverted example occurs at the end of the volume where Katerea Leviathan's attack on Kuoh Academy allows the Three Factions to form a peace treaty for good.
- Villain: Exit, Stage Left: After turning on Azazel and fighting Issei to a standstill, Vali decides to bail out and retreats with Bikou.
- We Will Meet Again: Once Issei overpowers Vali in volume 4, he vows that they will meet again. And sure enough, they do by the time volume 6 rolls around.
- You're Not My Father: Akeno is unwilling to forgive Baraqiel and outright refuses to acknowledge her relation to him.
