help me find this bl pls T_____T

there r 2 friends, they r college students. one have a fairly long hair for a guy (dark) and the other have short hair (light). one day light haired guy found a mysterious tin can in his bag. there was a note in the tin can. he decided to write a reply and put it in the tin can. the next day, he found a new note inside the tin can. he started exchanging notes with the mysterious person through the tin can and developed feelings for said person. then one day the person told him that he had to get surgery for his heart and the notes stopped (the person didnt die). anyways skip. turns out the person who he had been exchanging notes through the tin can was his friend all along but in the past. his friend knew who he was all along but kept quiet bc the timeline did not match yet.