Kai's manga / #childhood friends(15)

Boy finds a tin and finds out he can communicate to another guy from 3 years earlier. They become pen pals and he later finds out the guy was following his promises all along. Iori proposes to his childhood friend who promises to marry him when he turns 15 years old. Boy confesses to his childhood friend who thinks he's using him as practice to confess to the one he really likes

Guy has loved his straight friend for ages, confessing in high school. The friend promises to go on a date with him every year on his birthday until he finds someone else to love. 10 years pass and the gay guy decides he's had enough and tells his friend he's in love with someone else.