The Great Yotaro

(from ebookjapan):
Yotaro is the second son of a carpenter family. Yotaro is a cheerful boy in a family that does not get along well with each other. In the second half, Megumi makes an appearance! The first two volumes are gag manga, but from the latter half of the second volume, it turns into a school story with themes of friendship, justice, and hard work. The almost forgotten world of children comes back to life!

Note: Was simply Yotaro for the first two volumes. The title change begins with the third volume (following the shift in the second half of the second volume). Additionally, the very last arc, which spans about 2 volumes worth of content, is uncollected.