After a volume or two, Imai's brother shows up and gets together with Akkun's friend, so there are chapters about them, too. Also, every volume has short little chapters about a guy taking care of his boss who has mysteriously shrunk to doll size. (This has nothing to do with the main story, it's just in every volume.)

re: why you didn't buy it - you complained several times about how it had 5000 or so volumes. Also, s_vamp's complaints in her recent reviews about how annoying the brother is may have convinced me to keep my mouth shut about how I think the series is hilarious and adorable, but now I'm sorry I didn't try to convince you to buy it.