Manga that makes me think about what friendship is

I want to cherish friendship forever forever, but it is a cartoon that makes me think about what friendship is all about. It looks like a nice story, but it spoils a good story at the last punch.

Contents of cartoons are as follows.
Laugh IT Out
http://www.laughitout.com/

"Friendship with you makes me embrace various feelings"


"If you cry, I will also cry"


"If you laugh, I will also laugh."


"If you fly off the window, I will laugh again."