ingenuous

She was a "simple-minded, naïve, ingenuous girl", according to her first report.

His greatest hope for the future, Meghan is a high school senior at a horsy boarding school in the Washington area and possibly the most ingenuous girl since Alice in Wonderland.

All of this feels rather random, rather personal, rather ingenuous.

Even in the happiest times he’d made fun of my California accent, my secondhand overcoat and my room barren of tasteful bibelots, but in such an ingenuous way I couldn’t possibly do anything but laugh.

Wide-eyed and ingenuous, the character is a blank slate.