Maeda has just moved into his new apartment to live by himself. While unpacking, a cute middle school student named Chie Satonaka suddenly appears in his room. She introduces herself as his new landlord, which pleasantly surprises him as he has never seen a landlord so young. His excitement is boosted further when the gorgeous Reiko Shirai, who lives directly next to him, also introduces herself as his new neighbor. Ooyasan wa Shishunki! follows the everyday lives of Maeda and his newfound acquaintances, where each day presents itself as an opportunity for new events to unfold and new bonds to be forged. [Written by MAL Rewrite]

On his way home from school, Tatsumi sees a man collapsed near a lake. When he approaches him, Tatsumi notices something strange: the person in need of help is actually a beautiful merman named Wakasa! Because Wakasa's home has become too polluted to live in, Tatsumi graciously offers his bathtub as a refuge. With a boisterous merman as his new roommate, Tatsumi's normal life won't be returning anytime soon, not to mention Wakasa's aquatic friends—Takasu, Mikuni, and Maki—often show up uninvited, making them all quite a handful for the high school student. As he humors their curiosity for human life, Tatsumi sometimes finds himself enjoying their childish antics, but he will have to keep his cool if he intends to keep up with his daily life and newfound friendship. [Written by MAL Rewrite]

The infidelity of Eita Kidou's parents not only made his family fall apart, but also made him skeptic of love. Having no intention to delve into romance, Eita devotes his entire high school life to his studies in order to become a doctor. It did not take long for the beautiful and popular Masuzu Natsukawa to notice Eita's apathy. Tired of being the object of people's affection, she asks him to pretend to be her boyfriend, as she too feels disgusted at the notion of love. Eita, however, refuses—yet Masuzu has one trick left up her sleeve: Eita’s journal and threatening to post the embarrassing content online if he does not comply. Now entangled in a fake romance with the most desired girl at school, Eita's life is turned upside down. Whether envied by his peers or receiving a confession, he must cope with his newfound relationship and all the troubles that come along with it. [Written by MAL Rewrite]

Amatsuyu "Jouro" Kisaragi is a completely average second-year high school student who has two dates over one weekend⁠—with the student council president Sakura "Cosmos" Akino on Saturday, then with his childhood friend Aoi "Himawari" Hinata on Sunday. Sadly for Jouro, both girls proclaim their love for his best friend Taiyou "Sun-chan" Ooga, the ace of the baseball team. Accepting each of their requests for advice and guidance, he is now responsible for helping the two girls win the heart of the same guy. Unbeknownst to his friends, Jouro's friendly and obtuse image is all but a ruse designed to cast himself as the clueless protagonist of a textbook romantic comedy. A schemer under his cheery facade, he makes the best of this unexpected turn of events with a new plan: get Sun-chan to fall for either Cosmos or Himawari and take the other as his own prize. But Jouro's last-ditch effort is threatened by the gloomy, four-eyed Sumireko "Pansy" Sanshokuin, who surprises Jouro with not only her knowledge of his secret personality but also a confession to the true self he hid for all this time. Stuck in this hilariously messy situation, each of the five students must navigate countless lies, traps, and misunderstandings to come out on top. [Written by MAL Rewrite]