Among all the beasts that roam the world, there are unique types of "ultimate species" that harbor immense strength and magical prowess considered to be at the top of the power scale. As such, many humans covet their abilities, leading some of these species to the brink of extinction. As a beast tamer, Rein Shroud can employ the assistance of various animals for many tasks, such as reconnaissance and logistics. By virtue of his ability, he joins a party led by the vile and manipulative hero Arios Orlando, only to be banished after six months due to his uselessness as a non-combative class. However, unbeknownst to the team that cast him away, Rein is an exception among beast tamers. His potential becomes apparent when he meets Kanade—a cat spirit who is also one of the ultimate species—and is able to form a contract with her. With Kanade by his side, Rein sets out on his journey as an adventurer, steadily rising up the ranks and meeting more ultimate species along the way.

Second season of .

Third-year high school student Jirou Yakuin is in love with his childhood friend and classmate, Shiori Sakurazaka. Thus, he hopes to be paired with her for the "marriage practical": their school's practice of randomly selecting boy-girl pairs to live as pretend married couples while monitoring and rating them on how close they have gotten. Meanwhile, the lively Akari Watanabe wants to be assigned to her crush, the popular and good-looking Minami Tenjin. Much to their dismay, Jirou and Akari find out that not only have they been paired together, but so have Shiori and Minami! Determined to be with their crushes, Jirou and Akari strive to earn as many points as possible, as the top 10 pairs earn the right to switch their partners—so long as both couples agree.

Ittoki Sakuraba fails to understand why his mother, his uncle, and his childhood friend, Kousetsu, seem to take his security so seriously. Kousetsu constantly follows and observes him with no regard for his privacy, focusing only on keeping him safe every waking moment. But the consistent hounding starts making sense when an adorable second-year student at his high school, Satomi Tsubaki, asks Ittoki out on a date. Though initially innocent, Tsubaki's true intentions soon become apparent when Ittoki visits her house; she plans to assassinate him, and she is not alone. Surprisingly, the ones who come to his aid are his uncle and Kousetsu—donning their dark and deadly ninja attire. After Ittoki is escorted to safety, his mother reveals the truth: he is the 19th heir to a noble clan of ninjas known as the Iga, and the target of assassination by their rival clan, the Koga. In order to protect himself against this new threat, Ittoki must hone his skills at the only ninja academy remaining in Japan: the Kokuten Ninja Academy.