The episode opens where the previous episode left off. The devils and Lindo engage in a combat with Lord Nesta's minions. Jek takes Ritsuka back to Lord Nesta in order to proceed with the ceremony. While Lord Nesta is distracted by the battle, Ristuka uses this as an opportunity to escape by grabbing one of the tall candle holders and swinging it at his head. Jek rushes over to Lord Nesta as Ritsuka runs off, but Jek catches up to her. He grabs her by the scalp and slaps her across her cheek which briefly immobilizes her. He brings her back to Lord Nesta telling him to hurry while the moon is still full. Lord Nesta takes Ritsuka and prepares to bite her just as she recovers from being slapped. Her attempts to resist are futile and Lord Nesta tells her to prepare to be intoxicated by the ecstasy when being bitten. Ritsuka screams at him to stop until Roen interferes by using his magic to stop Lord Nesta. Ritsuka breaks away from Lord Nesta prompting Jek to run after her, but he is stopped by Rem who uses his powers to prevent him from recapturing her.
Ritsuka runs into Lindo's arms and he assures her that everything will be alright just as Rem appears behind him. Jek orders Lindo to stay out of this, claiming that Ritsuka is Lord Nesta's property, but Lindo replies that he won't let him touch his sister again. Jek mocks Lindo calling him a 'mish-mash dhamphir', and Lindo tells Rem to take care of his sister. Rem grabs Ritsuka by her shoulders and pulls her closer to him before teleporting away with her. They reappear on a deserted balcony, and Ritsuka awkwardly backs away from him, but he pulls her into a tight hug. He tells her to not do anything dangerous and when she looks up, she notices his relieved expression as he hugs her tighter. Rem then tells her when everything is over, there is something he wants to tell her, but he will definitely protect her. Meanwhile, Lindo is battling Jek using his exorcist and vampire powers. As they fight, Jek asks Lindo why of all things would he become an exorcist when he is the son of Lord Nesta. Lindo denies Lord Nesta as his father saying that he won't forgive anyone who tries to harm his sister. Jek seemingly gains the upper hand and lunges at Lindo to finish him off, but he gets trapped under an exorcist beam which Lindo had prepared earlier on. Realising that he had underestimated Lindo, he asks him how he did that, but Lindo tells him to begone from here and forever more before delivering the finishing blow. Jek ends up plummeting and gets impaled to death on a statue.
Lord Nesta scoffs and calls Jek incompetent until he notices Lindo and upon recognizing him as his son, he hypnotizes him. He tries to convince Lindo to become his ally by lying to him about how he had wanted the "grimoire" in order for him, Marta and Lindo to live together as a loving family. Under Lord Nesta's spell, Lindo begins to approach his father despite Ritsuka and Rem's warnings. However, Lindo is able to break free from the hypnotism and he stabs Lord Nesta through the chest with his claws. He angrily tells Lord Nesta that never in his life will he ever consider him as his father. He then pulls out his claws causing his father to collapse on the ground in a pool of blood. Seeing this, Lord Nesta's remaining minions retreat and Lindo rejoins the group. While Ritsuka reunites with her brother, Mage comments on how Lindo stole their moment to shine with Urie saying that it's not bad once in a while. Shiki says that seeing Lindo defeat Lord Nesta sent chills running down his spine, but Rem and Roen notice that something isn't quite right. Lord Nesta's voice is suddenly heard taunting Lindo for thinking he could be killed that easily and just as he says this, his corpse suddenly gets up and he is alive and well again.
This shocks everyone and Lindo quietly asks how is that possible. Rem says that Lord Nesta has hidden his real heart, and Roen explains that vampires who come from a long line of ancestors would possess this ability. Mage angrily yells at Lord Nesta, asking him where he's hidden his heart, but Lord Nesta tells him that they won't be able to find it. He suddenly unleashes a huge amount of energy which disorientates everyone and sends them flying into the walls. Ritsuka almost crashes into a wall, but Rem teleports himself behind her last minute causing her to crash into him instead. As everyone struggles to break free from Lord Nesta's spell, Lord Nesta declares that the grimoire is his and so will everything and the world. Ritsuka glances around at everyone, guilt-ridden of causing everyone to get hurt and not wanting to accept her fate, she decides to protect everyone this time. At that moment the needles of the clock strike twelve, signaling midnight. The grimoire is activated and a bright light is emitted from her body which stuns everyone.
When Ritsuka comes to her senses, she finds herself in the grimoire. As she looks around at her surroundings, wondering where she is, she suddenly spots a familiar looking dagger. She walks over to it and picks it up, recognizing it as Azuna's. Her thoughts are interrupted when she hears a distant heartbeat behind her. She turns around to see a tall black flower (Lord Nesta's heart) and she begins to approach it. Ritsuka is still glowing and she ascends the steps before heading to the right. Lord Nesta gets blinded by the light and when he looks up, he panics when he notices Ritsuka heading towards something and attempts to stop her by throwing the altar at her, but Rem destroys it with his magic. In the grimoire, Ritsuka stands in front of the flower and she quietly tells Lord Nesta to face death as a human. As she raises the dagger above her head she wishes Lord Nesta sweet dreams before plunging the dagger into the center of the flower.
There is a bloodcurdling scream and when Ritsuka looks up, she realizes that the grimoire has led her to a female statue which she has stabbed with the sharp scissors. Blood gushes out of the statue and when she turns around, Lord Nesta is slowly trying to approach her as he begins to deteriorate and become ashes just as the other devils and Lindo appear. The light begins to fade and as it disappears, Ritsuka suddenly collapses. Lindo rushes over to his sister, only to be stopped and become taken aback by surprise when Rem gets to her first. Rem frantically shakes Ritsuka as he cradles her in his arms while exclaiming her name. She slowly opens her eyes and Rem tells Ritsuka that he never wants to let her go again. The other devils insert their comments until they realize that the "grimoire" is gone. Urie is not bothered by this and he says that all they have to do is to wait another 615 years. From afar, Roen sighs that he might as well go look for something else for Lord Maksis.
As dawn approaches, everyone goes outside. By the lake, Rem proceeds to tell Ritsuka what he had planned to tell her after the battle: he loves her. He proves this by showing her the crowns they won from the evening party (see Episode 8). Touched by Rem's confession, Ritsuka rekindles her feelings for him by confessing that she too is in love with him. They then share an embrace and Lindo is shown watching from afar, sad that Ritsuka didn't reciprocate his feelings, but content to see her happy being with the man she loves. Rem tells Ritsuka with the "grimoire" gone, he and the other devils have no need to remain in the human world. He asks her to come live with him in the devil world and he tries to convince her by reminding her that she is part-devil, leading into their song 'Dance with Destinies'. Lindo vows to continue to show his love for his sister by protecting her, indicating that he is prepared to let go of Ritsuka if she chooses to live with Rem. As the sun rises on the horizon, Ritsuka declines to join Rem in the devil world because she doesn't want to leave her family.
Hearing this decision, the devils bid goodbye to Ritsuka, each promising to meet her again in the near future before returning to the devil world. Daylight begins to break and Rem sadly hands his king crown to Ritsuka. The moment she takes the crown from his hands, he starts fading away. Ritsuka begins to cry, but Rem goes up to her and they share their first kiss just as he disappears. After he is gone, Ritsuka hangs her head and quietly bids Rem goodbye, calling him her dearest devil. The aftermath then shows Ritsuka, Lindo, and Maria having breakfast together, indicating that life has returned to normal in the Tachibana family. Ritsuka is then finally seen dashing off to school, and around her neck is Rem's king crown which she has been wearing as a necklace: to symbolize her unending love for him with hopes of meeting him again one day. Elsewhere, Roen opens a pair of large doors revealing a book lying on the ground on top of a red cloth. The lock on the book unlocks itself and the pages fly open until a pair of blacked out pages is shown. Roen is finally heard welcoming Lord Maksis back, implying that the story is unfinished. The episode ends here.