help

okay all those new music related bls let me remember another one but i can't remember the name only the plot
it's about like someone, probably light haired, that travels thorough time (??? or reincarnated or transmigrated....) to the modern times where he meets another young man (probably black haired) and they make music together BUT it turns out that black haired young man is the grandson of the man that broke the light haired mans heart with a dumb misunderstanding and then you find out he killed himself and the grandfather of the man always had regrets..... but idk anything else ... does anyone know the name