The overall story concept is really heart-touching and warming it was more of a emotion love related story then an general rom-com story you find.
While reading the summary of the manga you can get the idea was the story could be and it’s really worth reading.
There are two thing which I specifically don’t like (might contain slight spoilers)
Even though there is a tag of science fiction but still the concept used in this manga to send laters to the past selves is concept not related to the story, it doesn’t feel like it somehow.
I know there is no other way to send the letter in the past until there is some kind of time-machine is there and then it does end up in science fiction category so that can’t be helped.
Secondly and most important one that in the end there is no story after their love confession (again I will not share much detail, so you’re safe).