The first errand (hajimete no otsukai) refers to the first time children are sent on an errand by themselves, usually to buy groceries at the local store, and is a fairly common milestone for families in Japan. It was also the subject of a non-regular, documentary/reality television series broadcasted by Nippon TV (available on Netflix since April 2022 under the title "Old Enough!")
Common elements in images include dragging a grocery bag with items spilling out, crying, getting lost and carrying siblings. Occasionally there will be an older family member discreetly lurking nearby. Images with this tag do not need to be the literal first time a character goes on an errand.