The film tells the story of a new transfer student interested in her surroundings, and a song that brings happiness to her and her classmates.

Once upon a time, the demon lord Rchimedes spread terror throughout the world, until he was eventually sealed away by the legendary hero Creasion. Since then, a thousand years have passed peacefully. However, a mysterious hole has opened up between the demon and human spheres, and countless demons have surged into the human realm once more. Coming to the conclusion that Rchimedes would soon return to wreak havoc, a human king summons the possible descendants of the legendary hero—all 75 of them. Unfortunately, after so long, it was too difficult to pinpoint his true descendants. Among the lionhearted prospects is the amateur adventurer Alba Frühling. His skills may not be top-notch, but he is accompanied by the talented soldier Ross, who helps the young hero whenever he is in a pinch...or at least, he is supposed to. Though undoubtedly a skilled warrior, Ross is actually both sarcastic and sadistic, and hence revels in Alba's suffering. Senyuu. is a comedic adventure following the unlikely duo as they struggle in their endeavor to defeat the demon lord, meeting various eccentrics along the way. [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]

One day, Manaka Junpei walks to the roof of his school and encounters a beautiful girl falling down from above him and accidentally exposing her strawberry panties. The embarrassed girl runs away before Junpei can find out whom she is. He wishes to become a filmmaker, and this whole experience seemed like it would make the perfect scene in a movie. And so he goes on a search for the girl with the strawberry panties in order to reenact it all on film. But he will soon discover that finding that one girl will not be that easy... (Source: ANN)