Manatsu no Blue

Natsuno Sarasa is painfully shy and is afraid to speak her mind, but as the summer music festival rolls around the corner, she prepares herself to make some new friends. However, just when she begins to lose hope, a boy in her class asks her for one of her tickets to the festival. Hourai Yayoi isn't the kind of new friend she was expecting to make, but...?

(Source: Lucia Rose Scanlations)