A Perfect Day for Love Letters(2001)

Koibumi Biyori

Every letter the mailman delivers brings a new chance at love. With wit, humor, and mystery George Asakura leads us through a series of brief tales of affection, rejection, miscommunication, and connection that are sure to charm the romantic inside you.

(Source: Del Rey)

Included one-shot:
Volume 2: Natsu no Awa

Note: Won the 29th Kodansha Manga Award for the shoujo category in 2005.