The story revolves around Tomoya Mizuhara, a 13-year-old boy who suddenly gains a big sister when his father remarries. 17-year-old Ichika is a little strange, and her affection for Tomoya is rather overwhelming, if not scary. On top of things, Ichika's friend Ruri is the ultimate sadist. Then there is Ichika's big-breasted quarter-Japanese friend Marina. (Source: ANN)

Onyankopon watched over people long ago, but one day an old woman accidentally hit Onyankopon in the head with a mallet while mashing yams. Since then, Onyankopon has been nervous about greeting people directly, and so sends subordinates to speak to them and solve their problems. He will use Afrobeat and dance to help Japanese high school girls with problems such as dieting, love, and cramming for exams. (Source: ANN)

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]