Here's arguably one of the most popular manga on this board (not counting the many ones that gained popularity through their anime adaptation).
>Punpun Onodera is a normal 11-year-old boy living in Japan. Hopelessly idealistic and romantic, Punpun begins to see his life take a subtle—though nonetheless startling—turn to the adult when he meets the new girl in his class, Aiko Tanaka. It is then that the quiet boy learns just how fickle maintaining a relationship can be, and the surmounting difficulties of transitioning from a naïve boyhood to a convoluted adulthood.
Also, I'll be having this as the OP image from now on because I don't like the way the volume covers look. Sorry. If many of you are against this decision, I'll be sure to return to using the volume covers.