Aitsu no Daihonmei
Sato the schools prince meets Yoshida from elementary school. Yoshida was the tall kid who alway helped the bullied fat kid Sato. Both of their looks have dramatically changed. After Sato went to a special school for fat kids in England he lost weight and grew tall. Whereas Yoshida stopped growing early and is now the shortest kid.
Mobius Strip
Barairo no Hoo no Koro
the school days od paul and morgan before J no subete: http://www.mangago.me/recommend-manga/j_no_subete/
Like a Sugar
spin off of the second couple (the friends, classmates): Bitter like light: http://www.mangago.me/read-manga/bitter_like_light/
Doushiyoumo Nai Keredo