Sanbun no Ichi.

is a japanese manga series written by Matsuzawa Mari. It began serialisation in Comic Yell! and was transferred into Manga Time Kirara Forward from the August 2009 issue.

The series was released under 3 volumes from July 2008 to October 2009.

Synopsis
Yuzu, Aoi, and Kaede have been childhood friends since they were little. When I become a junior high school student, the relationship between the three people gradually changes ...!? Mari Matsuzawa's Triangle Junior High School Diary, which depicts the swaying mind and body between adults and children ☆

(Source: MU)