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.

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.

During the summer holidays, energetic Hana Uzaki spent most of her time accompanying her lonesome upperclassman, Shinichi Sakurai. Now that school has resumed, Uzaki's teasing continues to ramp up, much to Sakurai's constant annoyance. Nevertheless, no amount of ridicule can damage the pair's relationship—which only seems to be getting better as their college days fly by!

Yearning to make friends and perform live with a band, lonely and socially anxious Hitori "Bocchi" Gotou devotes her time to playing the guitar. On a fateful day, Bocchi meets the outgoing drummer Nijika Ijichi, who invites her to join Kessoku Band when their guitarist, Ikuyo Kita, flees before their first show. Soon after, Bocchi meets her final bandmate—the cool bassist Ryou Yamada. Although their first performance together is subpar, the girls feel empowered by their shared love for music, and they are soon rejoined by Kita. Finding happiness in performing, Bocchi and her bandmates put their hearts into improving as musicians while making the most of their fleeting high school days.