Help me find this pls

ok i remember reading this BL but i forgot the name. it’s about this guy that likes this girl that he saw on a train so once he thinks he finds out her name he gives her a love letter but the name he thought was hers was the girls brother. So the brother and the boy start dating, i remember the one of the boys had long hair but pls tell me the link or name once you find it ٩(๑❛ᴗ❛๑)۶