Koibito ga Ubu Sugite Komaru

Hasegawa is a bit of a high school nobody. He's plain, quiet, and unassuming...so it's a huge shock when Hiyama, the sunny social butterfly of their class, suddenly confesses to him! But how do you date a classmate you've never even spoken to before? By starting a good old-fashioned diary exchange, of course! Entry by entry, two romance novices find a way to bridge the gap between them—and maybe even discover love along the way...
(Source: Yen Press)
Note: Includes two extra chapters.