From MangaHelpers:
At school, Kamazaki Yuu feels as though there is a circle drawn around her, a line that no one will cross. A part of it is because her face looks mean, and another part of it is because she's rather socially awkward, but the largest part of it all is that she has earned a reputation for being really bad-tempered and violent to the people around her.
This all changes in her second year of high school.
The cute, friendly, and popular Kume Asami one day inexplicably crosses that invisible line and decides to be her friend. Kume introduces "Kama-chan" to friendship and to the 5-man futsal club that meets on the school roof. As Kama cautiously enters Kume's club, she may find herself able to grow past the bad expectations people have of her, and enter into a new, happier, high-school life.