Kimi to wa Gokai kara Hajimarimashita ga

Overview

High school student Miike Kazuya, who is a good person but often pessimistic 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 even though it was supposed to be, Since he read the name wrong, the girl’s older brother. It’s given to Utakane Hifumi-san… What will become of the acquaintanceship that started from a mistake? Youthful pure love (heart) open the curtain!! (Source: Houbunsha, translated)

Source: AniList