RandomC did try to classify the characters like this last week.

Anaru is Envy (envious of Menma), Jinta is Wrath (hates everyone), Poppo is Sloth (the weakest sin, is too carefree), Yukiatsu is Lust/Gluttony/Greed (a triple whammy, self-explanatory), and Tsuruko is Pride (not much is known about her, but she certainly sees herself as above everyone in terms of the Menma issue, hence pride)