Sentimental Graffiti

The protagonist, Tanaka Ichirou, is a high school student who, prior to the spring vacation of his third year, receives a letter simply stating "I want to meet you." During middle school, his frequent transferring of schools allowed him to form unique relationships with various girls. In order to search for the sender of the letter, he travels nationwide to various places, and meets the 12 girls of his memories once again.

[From Wikipedia]