Kimi to wa Gokai kara Hajimarimashita ga

Kazuya Miike, a good-looking but gloomy high school student, writes the first love letter of his life. The love letter's recipient is a female high school student he happens to see on the commute to school, "Hifumi-san." Or it was supposed to be, but since he read the name wrong, it was given to the girl's older brother, Hifumi Utakane... What will become of the relationship that started from a mistake? (Source: Houbunsha, translated)