Straightforward, candid, open, and frank. (adjective)
Examples of word ingenuous
Criminals on trains often adopted what the researchers described as ingenuous tactics in their activities.
George Kembel, head of the Stanford d. school, calls the ingenuous device a $19,975 cost-savings.
It is Jan who is "regurgitating" the kind of ingenuous drivel that a million half-arsed career pundits are lining up to declare on CH4 news and Newsnight.
You needn't say 'ingenuous' isn't a real word, because it is.
If to the day of his death, after mortal disenchantments, the impression he first produced always evoked the word "ingenuous," those to whom his face was familiar can easily imagine what it must have been when it still had the light of youth.