The variety of comments for this manga are interesting to say the least-
I resonate with this piece, even if the dialogue is convoluted or too abstract for me to really comprehend.
Maybe the author wanted to write about how people can live a fulfilling life, without thinking consciously about every single action. The Adult has a good moral compass and is witty as a Child.
Despite how insipid her apartment is, the Adult seems to have found her own answer, even if, as someone else describes it as, "fear of being an outcast," at least it's not debilitating. Maybe in her later years, she'll have saved enough to pursue whatever interests her. The monotonous truth is that she's living, and there's strength in that.