The episode opens where the previous episode left off. The grimoire's light soon fades away and Ritsuka suddenly passes out. Lindo catches her from behind and quickly uses his exorcist powers to create a temporary barrier to mask the grimoire's scent. He then picks up Ritsuka and sadly glances as Azuna's lifeless body as he leaves with his sister. A while later, Urie, Mage, and Shiki arrive at the place where Lindo, Azuna, and Ritsuka were ambushed by the vampires. Urie comments on how he had never imagined that Ritsuka was the grimoire all along when he was convinced it was a book. Mage curses at Rem for lying to them and Shiki comments on how Ritsuka being the grimoire sent shivers down his spine and that he knew she was special. Urie wonders out aloud what Rem was trying to protect and Mage complains that he cannot track her scent. Shiki approaches Azuna's lifeless body and taunts her for not being special until he notices that Urie and Mage have left without him. After he flies off, Rem appears and as he glances at his King crown, he asks himself what he is waiting for. It is then that Rem has finally decided that he loves Ritsuka and wants her more than he wants the grimoire.
Meanwhile, Lindo has taken Ritsuka to the Exorcist Association for protection. The head of the association sympathizes with Lindo about Ritsuka being the grimoire and praises him for choosing the society to safe keep her. He also tells Lindo that if Azuna were still alive, she would have been rewarded as well. Lindo is then handed another ring of the Sacred Lux and he thanks the exorcists for their kindness. In another room, Ritsuka is in bed tossing and turning while exclaiming Azuna's name until Lindo takes her hand which wakes her up. When asked where she is, Lindo tells her that this is the Exorcist Association, and they'll be staying here until after her seventeenth birthday. She frantically asks about Azuna, but Lindo sadly informs her silently that Azuna is dead. Overwhelmed with guilt, Ritsuka exclaims that it was all her fault and she would be better off dead. Lindo tells Ritsuka not say such things because Azuna would not want her to think like that. He then hands her Azuna's rosario and reveals that Azuna kept fearing that Ritsuka would eventually find out about her being an exorcist and would not want to be friends with her anymore. However, Ritsuka accepted her as she was which made Azuna very happy to be able to openly protect her and he convinces his sister to not think of her best friend's death in vain.
Ritsuka soon goes back to sleep and Lindo places the ring of the Sacred Lux on her finger since the grimoire's light destroyed the first one she had. At that moment, Ritsuka briefly awakens and she tells Lindo to not go anywhere. This startles Lindo and he agrees, promising to always be by her side. Ritsuka falls back asleep and Lindo gives her a kiss on the forehead before leaving the room. Lindo then goes to a chamber in the society where he undergoes a purification process. Hot oil is poured down his back in order to help him suppress and control his supernatural instincts. Meanwhile, Urie, Mage, and Shiki are at Tokyo Tower, still having no luck in finding Ritsuka. Urie tells Mage that he shouldn't rely on his nose all the time because he can already tell that Ritsuka is behind a powerful barrier. Mage spots the Exorcist Association and deduces that she is in there, while Shiki wonders out loud if it really is a safe place for Ritsuka. Back at the association, Lindo returns to the room only to be shocked when he finds the bed empty and his sister nowhere to be seen. Elsewhere, Ritsuka is brought to a dark room where all the exorcists are gathered. Disturbed and confused, Ritsuka asks what is going on. The head exorcist tells Ritsuka that she about to undergo a ceremony that will cleanse her. She asks where her brother is, but the head exorcist insists that it would be better if Lindo was not involved before gesturing her to take a seat.
She reluctantly sits in the chair before her and an exorcist brings out a tray of sharp tools while another brings out some chains. Realising the danger she is in, Ritsuka tries to escape, but the exorcists force her back in the chair as they attempt to proceed with the ceremony until Lindo bursts in. This allows Ritsuka to break free from the exorcists and she runs into her brother's arms. Lindo confronts the exorcists, demanding to know what they were trying to do to his sister, so the head exorcist explains that the objective to protect the world is to eliminate the grimoire, in other words, they were going to kill Ritsuka. Lindo tells them that they're mad, but one of the exorcists tells him that it's only natural for a 'dhampir' like him to not understand this. This shocks Ritsuka and upon noticing her confused expression, another exorcist asks her if Lindo hadn't told her about it yet. He sneers it's a pity and tells her to listen carefully. He reveals to Ritsuka that her brother is a 'dhampir': a person who is born half-human, half-vampire. The head exorcist tells Lindo to hand Ritsuka back to them so they can continue their ceremony, telling him that he'll eventually understand if he thinks rationally because they believe the well-being of the world is the priority. Angered that they had betrayed his trust, Lindo tells them to die instead.
He then kicks over a candle and uses his exorcist powers to set the room on fire. Lindo then grabs Ritsuka and he tells her that they're running. They exit the association and are pursued by the exorcists. The exorcists declare that their goal now is to kill Ritsuka, but they are stalled by Urie, Mage, and Shiki who tell them that they are not going to let them kill her. Meanwhile, the siblings run to a Japanese temple where Lindo tells Ritsuka that they will hide here until daybreak. While resting, Ritsuka asks Lindo if what the exorcists said about him is true. Lindo confirms this and reveals to Ritsuka that his father was a vampire, who conceived him with a human. Ritsuka frantically asks him if that must mean she's a dhampir as well, but he assures her that she isn't one. He then reveals to her that the reason why she isn't like him is; they aren't really siblings. The scene then changes to a flashback where a young Lindo is visiting Marta with some flowers and a drawing. He addresses her as his mother, but Marta, overwhelmed by her illness insists that she has no children and she asks Lindo who he is, claiming that her son had been "eaten by a monster". Marta soon succumbs to her illness and during her funeral, Maria gently tells Lindo to be a big brother to her young daughter, Ritsuka from today onwards.
The flashback ends and Lindo reveals to Ritsuka that he is actually the son of their deceased maternal aunt, Marta. The reason for her illness was when she discovered that she was going to bear a vampire's child, thus rejecting Lindo as her son after he was born. Lindo then tells Ritsuka that he wasn't alone since he had her, their grandfather, and her mother who were always there for him. Another flashback shows a young Lindo and Ritsuka playing in the back garden of their grandfather's house. Ritsuka catches a dragonfly but trips while she dashes over to Lindo to show it to him. As he helps her up, he notices a bloody scratch on her knee causing his vampire instincts to convulse. Not wanting to hurt Ritsuka, Lindo makes an excuse that he caught a cold, but Ritsuka rushes over to hug him, saying she will warm him up much to his surprise. The scene then changes to another flashback where Lindo is taken to a cave by their grandfather who tells him that this is a training which will help him control the evil blood running through his veins. As he closes the door, he assures Lindo that he will definitely succeed. Lindo becomes scared until the door opens and Ritsuka rushes in claiming that she has come to save him. He tells her that he'll be alright because he's taking special lessons to have a strong heart and to protect her.
The flashback ends and Lindo admits to Ritsuka that he felt anxious about having to keep quiet about this from her. Ritsuka tells him not to be because she now understands why he did everything for her up until now. She then takes his hand and states that even if they're actually cousins, and even knowing he's a dhampir, he will always be her brother and her precious family no matter what. Touched by Ritsuka's acceptance, Lindo embraces her as she thanks him for protecting her. Lindo tells Ritsuka that she gave his life meaning when he kept belittling himself as an ambiguous being before confessing that he is in love with her. This shocks Ritsuka and Lindo moves in to kiss her, only to be interrupted when the door slides open revealing Rem, resulting in an awkward atmosphere. Assuming that Rem has come to obtain Ritsuka as the grimoire, Lindo firmly tells him that he will keep Ritsuka safe. Rem struggles to explain his reason for being here and Ritsuka notices his troubled expression, but Lindo tells her not to be deceived. He tells her that the devils do not have a speck of truth in whatever they say or do.
They go outside, where Lindo transforms and he tells Rem that they will settle things once and for all. He also tells Rem that he will also make sure that he doesn't lay another hand on his sister. Rem hesitantly accepts Lindo's challenge, leading into their song 'KETTO ~Unyielding Conflict~' ("KETTO ~Yuzurenai Semegiai~" KETTO ~譲れない せめぎあい~). During the battle, Rem soon gains the upper hand and severely injures Lindo. When Lindo falls onto his knees, Rem tells him to give up, claiming that Lindo cannot protect Ritsuka. Lindo insists that he would die for his sister prompting Rem to agree to grant him his wish. Just as he is about to deliver the finishing blow to Lindo, Ritsuka exclaims his name causing him to stop as she rushes over and places a protective arm around her brother. Convinced that Rem still only sees her as the grimoire and is willing to kill people just to get it, Ritsuka tells him that he truly is a devil. Rem tries to speak but blinded by her anger, she cuts him off saying she is done letting him hurt the people closest to her before tearfully yelling that she hates him and despises him. This shocks Rem and Lindo uses his exorcist powers to repel him. Ritsuka quietly tells Rem to never come back and he leaves heartbroken.
Lindo transforms back into his normal self and Ritsuka notices that he is bleeding. She tells him that she'll get him to the hospital, but Lindo refuses. He tells her that things will get complicated if the doctors and nurses found out he is not entirely human. Elsewhere, Rem is on a tall building watching Ritsuka and Lindo leave the temple from afar, regretting everything he had done and not being able to tell her his feelings. Ritsuka brings Lindo to Shikō Academy where she uses the school's infirmary to treat his injuries. While he is resting, Ritsuka reaches into her pocket and pulls out Azuna's rosario. She quietly says that she doesn't need the grimoire's powers as she places Azuna's rosario around her neck to commemorate her best friend. As dawn breaks, she decides that she will live in order to protect her family. Ritsuka then opens the window and wanting to remain true with what she said to Rem, she discards her Queen crown into the fountain in an attempt to erase her feelings for him. Meanwhile, Jek visits his master, Lord Nesta to inform him that he is planning to seize Ritsuka. Lord Nesta tells him that he is counting on him and Jek asks him what he intends to do with Lindo. Lord Nesta replies that Lindo's life is entirely on the palm of his hands. The episode ends here.