Issei Hyoudou, a former human reincarnated into a Devil, isn't sure how much more punishment he can take. To recap, he had been sent to a house to make a contract, only to find his client had been murdered by an insane priest and exorcist named Freed Sellzan, who then attacked him. Freed shot him in the leg with blessed rounds and slashed his back with a sword of light. Since Devils are vulnerable to Holy energy, these wounds have incapacitated him. His friend, the nun Asia Argento, who had been working with Freed and unaware of his insanity and cruelty, arrived and tried to help Issei, but Freed tore her shirt open and tried to rape her. Enraged, Issei summoned his Sacred Gear, a red gauntlet on his left hand, and punched Freed. Just as Freed was about to kill him, his Master Rias Gremory and her peerage, consisting of Akeno Himejima, Koneko Toujou, and Yuuto Kiba arrived and forced Freed to back off.
Koneko sniffs the air and detects that multiple Fallen Angels are coming to the house, so they need to get out of there. Freed brags that they are doomed, but Koneko shuts him up by throwing a chair at him. Issei can't even stand because of his injuries, and stares at his gauntlet wondering what good is it. Rias orders Akeno to prepare to teleport them out and Koneko to get Issei. While Akeno forms a red magic circle on the floor in the shape of the Gremory family crest, Koneko effortlessly picks up Issei despite her tiny body and carries him to them, and Kiba stands guard with his swords. They stand in the circle and prepare to teleport away, but Issei notices Asia is still on the floor, trying to hold the remnants of her shirt together. Issei calls out to take her with them, but Rias sadly says the teleportation circle only works for members of her household.
Horrified, Issei tries to reach Asia, but can't break Koneko's grip. He screams Asia's name and then desperately screams at Koneko to let go of him because he can't leave her at the mercy of the same Fallen Angels who callously murdered him back when he was human just because he had a hidden power. Unnoticed by anyone, his out of control emotions start to awaken his Sacred Gear's power and he starts to resonate with someone from another world. Asia tries to tell him that she'll be okay, but Issei then starts begging for someone, anyone, to save Asia.
Meanwhile, far away, Valerie Tepes, a half-human, half-vampire, is shocked when her Sacred Gear, Sephiroth Graal, activates by itself. Three golden cups manifest on the table before her, each filled to the brim with magical power. As she stares, wondering why her Holy Grails have appeared, she is suddenly bombarded by someone else's memories, of a king with an unrewarded life of duty and hardship, with a wish that would alter reality itself. Of an endless moment on a hill of swords. Out of all these thoughts, she hears this the loudest, "I will claim the Holy Grail."
A wave of energy washes over Issei and he wails in despair, but when it passes, he finds that everybody is still in the room. Surprised, Akeno says she has lost control over the circle. They look down and find that the circle has turned blue and has changed into a different design. They all jump out of the circle and Koneko puts Issei down and stands guard over him.
Four Fallen Angels, three females and one male, distinguished by their black feathered wings, enter the room. Issei is horrified to find one of them is Raynare. A few days ago, the raven haired beauty had disguised herself as a student named Yuuma Amano and asked him on a date. He happily accepted, but at the end of it, she revealed her true form and that she never cared about him and only went out with him to confirm his hidden powers before murdering him, forcing Rias to reincarnate him as a Devil. In the present, Raynare looks the Devils over, and when she sees Issei, she laughs and says she can't believe someone would bring that "worthless fool" back to life, breaking his heart even more. She gathers energy into her hand and says she should finish what she started. The male Fallen Angel gets everyone's attention and points at the circle, asking what that symbol is. Suddenly, a great burst of power erupts from the circle, filling the room with light.
Valerie stares at her three Holy Grails, which glow with rainbow colors. One cup summons a soul from another world, the second cup creates a body for it, and the third cup fills it with unique powers. Valerie has used the Grails to revive the dead before, but she has never seen this. The cups stop glowing, their task complete, and Valerie collapses, since the Grails channeled their power through her and her body was overwhelmed by the strain. While waiting for her attendants to find her, she shudders in fear and thinks, "She's coming for me."
When Artoria Pendragon materializes in the room, standing in the magic circle, everyone is stunned. Everything about her, her clothes, her armor, her hair that looks like gold spun into thread, and her face are absolutely flawless. The Fallen Angels quickly become jealous that her beauty surpasses their own. Though she is barely over five feet tall, her charisma makes her look grand and majestic, and the effect is magnified for Issei since he is on the floor. Asia is enthralled by her beautiful emerald eyes which scan the room. At first, the two sides assume Heaven sent an Angel to be a representative in the three-way conflict between Angels, Fallen Angels, and Devils, but then they realize she is not an Angel as she has no Holy energy they can sense. The Fallen Angels become outraged that they were momentarily jealous of a mortal, while the Devils try to find out what is going on.
Artoria looks around the room. Her spiritual senses tell her that all but two people in the room are not human. On one side of the room are a group dressed like Japanese high school students, which she recognizes from her time with Shirou. On the other side are four people floating in the air with black feathered wings that don't have to flap. The two humans are wearing religious outfits. She sees Issei on the ground and stares at his red gauntlet, feeling a strange connection to it. He stares at her in complete awe and confusion; combined with his injuries, she judges that he was the one calling for help. She then looks at Asia and judges that she is Asia, the one whom the boy begged to be saved because of the tears running down her face and the condition of her clothes. She decides to give her traditional greeting from when she is summoned. She faces Issei and says, "I ask you, are you..." Everyone is transfixed by her beautiful voice, but in the middle of her sentence, Issei gets up and charges.
Issei was just as entranced with Artoria's appearance as the others, but snapped out of it when he remembered Asia. He may be a pervert, but he cares about his friends. He is thankful Artoria is wearing a conservative outfit as this means he is not as distracted. Noticing everyone is distracted by Artoria, he gets up and runs toward Asia, fighting the terrible pain of his injuries. Just as he reaches her, Freed suddenly stands over them and swings his sword down. While Issei covers Asia with his body, the Devils cry out for Issei. Rias prepares a blast of her Power of Destruction, Akeno prepares a lightning blast, and Kiba prepares his swords, but they all know they won't make it in time. Koneko, who has no long range attacks, laments taking her attention off Issei. Issei thinks to himself that he is willing to die all over again to protect Asia, while trying to ignore the fact her now bare chest is pressing against him. Artoria says she guesses that answers her question, it is him. Confused that he is still alive, he looks up to see Artoria extending her arm as if she is holding something. Freed's sword has seemingly stopped in midair; he grits his teeth and presses down, but cannot budge. The others in the room realize Artoria stopped his sword somehow, and though she doesn't have Holy nor Demonic power, she has a lot of raw magical potential and strength, as she is not straining at all to hold Freed's sword in place. Artoria gives Issei a smile. He is mesmerized; before she had a stoic look and he thought she could not be any lovelier, but he was wrong.
Freed angrily calls Artoria a bitch and says she should have waited her turn. He points his gun at her head and fires, but she lightning fast holds her hand up and the bullet bounces off something invisible. She then kicks him in the gut and launches him through a wall. From the ground, Issei is able to look up her skirt and is disappointed to find she wears trousers under it. He then sees the floor her other foot is standing on is cracked, further demonstrating the force she exerted. Artoria asks Issei if he can run. His adrenaline rush is spent and he can barely move, but then Asia puts her hands over his leg wound and activates her Sacred Gear, pouring healing energy into the injury. Issei tries not to think about how Asia's chest is exposed again and says he can run as the injury is completely healed. He still has the wound on his back, but he can manage. Artoria tells him to take the girl to safety while she eliminates the threats.
Insulted, Raynare says beating a worthless human like Freed doesn't mean she is strong. The Fallen Angels all summon spears of light into their hands. Issei takes Asia's hand and starts to lead her outside, confident that his mysterious savior will protect them. Rias protests, saying this area is Gremory territory and killing Fallen Angels here might restart the Great War. Artoria says fine, she won't kill them. Rias says that's not the point and asks who or what she is. A terrified Koneko says she is a dragon. At this announcement, everybody in the room is stunned and stares at Artoria wide-eyed. Unfazed by the announcement, Artoria repeats to Issei to get Asia out of there, and she will wait here for his return. He thanks her and he and Asia step outside into the night. He thinks to himself that is twice that he owes a beautiful woman, first Rias and now this stranger.
Hearing Issei thank her makes Artoria smile briefly. It is a knight's duty to protect whom they have sworn an oath to. Rias, realizing the situation is out of her control, tells her peerage to follow Issei and keep him safe. The Devils exit the house. Raynare tells her comrades to retrieve Asia while she handles Artoria. She charges Artoria with her spear while the others fly toward the front door, but Artoria swiftly hits one of them and knocks him into the others, leaving them tangled on the floor. They angrily get up and Artoria stands between them and the door, saying they won't leave unless she allows it. Artoria thinks of Issei and how his determination to save Asia reminds her of Shirou. She says to herself, "You are my Master."
