Tsuishin Soragoto ni Hohoenda Kimi e

It is the first day of the second year of high school. Shinoyama Masaki meets Haruka Kazama, a beautiful honor student who he had absolutely no recollections of. He begins to probe her to find out who she really is, but for some reason, Haruka's behavior is deeply connected to the contents of a postcard that Masaki casually wrote.

(Source: Fantasia Bunko, translated)