haha.. pls help :')

i forgot the name of this manga, my brains lagging so bad, but abyways here was the story: So this kid/18 year old boy has a family that runs beach houses? and there he meets an older guy who he initiially hates so much but that same summer they get really close and the kid starts having feelings for the older ojii-san lmao. the older dude also lost his previous lover/crush in a car accidnet?i thin also i remebr them sharing headphones and then the kid tells the older dude to wait for him on a specific date so they can reunite AGHHH itd be apprexiated if any of yall knew this thanks ♡