Starting from the familiar fairy-tale opening, "Once upon a time," the speaker wonders whether the phrase is really a sign of fiction. If something truly happened, they reason, then "once upon a time" should fit it just as well. From there the thought spirals into something bigger: maybe everything is made up, and maybe we aren't even here at all.
The speaker doesn't seem thrilled by this idea. They call it "something to think about" but also "scary," and the fear comes from loneliness. If the people we meet and the memories we carry aren't real, then we are completely alone. The last lines add a bleak detail, describing a world where people are "already desperate," which suggests that things are hard enough without that extra emptiness.
The mood is quiet, uneasy, and a little vulnerable. Short, plain lines and simple wording make it feel like someone thinking aloud, unsure and slightly afraid of where their own question leads.