At the peak of a steep hill, in the picturesque Onomichi town, stands a building with a lounge open to all. An unusual group of friendly people gathers there, each with their own stories to tell.

Tasuku Kaname is a troubled high school student who is prepared to commit suicide because his classmates found out that he might be gay. As he questions his existence, the sight of a mysterious woman jumping off a nearby building leaves him utterly startled. He rushes to the scene only to discover her unharmed, soon learning that she is the owner of the aforementioned building, known to everyone as "Anonymous."

Anonymous notices Tasuku's nervous temperament and offers him an ear if he is willing to share his problems. While speaking to her, he realizes that the most painful thing is his inability to accept his sexuality. Emotional and heartfelt, Shimanami Tasogare is a realistic take on the struggles of Tasuku among other lesbian, gay, bisexual, and transgender people in coming to terms with their selves.