After Jinta and Suzune ran away from their home as children, they were taken in by Motoharu—the virtuous sentinel of Kadono Village—and his daughter, Shirayuki. The settlement was ruled by its shrine maiden, Itsukihime, whom only a select few were allowed to interact with. When Itsukihime passed away, Shirayuki was appointed in her place. Wishing to stay in contact with her, Jinta worked diligently for years and was finally selected as the next sentinel. As the protector of the village, Jinta's duty is to eliminate any threats. One day, he encounters a demon in a nearby forest. At the end of the battle, the demon makes a proclamation about the destined ruler of all demonkind. He attaches his severed arm to Jinta, turning him into an unaging demon man. By the time Jinta comes to, Kadono is on fire. Suzune has transformed into the demon from the divination, and due to a series of misunderstandings, she murders Shirayuki and flees. Devastated, Jinta cannot forgive Suzune for her actions; he departs on a journey to find her. As Jinta travels around Japan across the eras, he endeavors to protect as many people as possible from aggressive demons. In his quiet moments, he contemplates what he should do when he once again faces his childhood friend.

After the success of his crowdfunded movie featuring the woman of his dreams, Chizuru Ichinose, university student Kazuya Kinoshita resumes his life of lies and deception. Although he pretends that he has been in an ideal relationship with Chizuru for more than a year, Kazuya still mostly sees her through a rental girlfriend company's services. However, after Kazuya attends a private party with Chizuru, he reaches the decision to finally confess his feelings to her. Unfortunately for him, his trial girlfriend Ruka Sarashina and his ex-girlfriend Mami Nanami continue to complicate his already messy attempts at romance. While he is forced to keep up his facade, Kazuya is under pressure to find a solution to his ever chaotic love life.

A lot has happened for Nagi Umino and Erika Amano: they were swapped at birth, learned of their engagement, and have started living under the same roof. The two now share their home with Nagi's sister, Sachi, and his crush, Hiro Segawa. Despite this unusual domestic situation and frequent quarreling, the group is beginning to settle into a life together. However, the return of Nagi's childhood friend Ai Mochizuki to Japan complicates things. Ai suddenly declares her intention to marry Nagi, and although he turns her down, she is committed to having him all to herself. Now with four girls around, each with their own thoughts about him, Nagi must figure out his own feelings and the best way forward.

Following the massive operation that led to the confinement of recent recruit Kafka Hibino, otherwise known as Kaijuu No. 8, the Defense Force has been puzzled by how to deal with him. Kafka is the first kaijuu to side with humans, and after careful consideration, he is eventually transferred to the Defense Force's First Division in the hope of adding his power to the strongest division, capable of handling any threat. However, some people are still doubtful about Kafka, and he must prove his worth in the next mission. Kafka and the First Division are soon dispatched when a massive horde of ant-like kaijuu begins wreaking havoc. Thanks to the combined strength of Kafka's friend Kikoru Shinomiya and their captain, Gen Narumi, the mission seems to progress as it should. However, when Kafka fails to transform into his kaijuu form, the dreadful Kaijuu No. 9 joins the battle with only one goal—to eliminate him and steal his power. Although the situation is looking grim, Kafka must overcome his most difficult trial yet with the others if he wants to keep pursuing his dream: fighting side by side with his childhood friend and Third Division captain, Mina Ashiro.