From Longman Dictionary of Contemporary Englishguilelessguile‧less /ˈɡaɪl-ləs/ adjective HONESTbehaving in an honest way, without trying to hide anything or deceive people SYN open
Examples from the Corpus
guileless• Distressing, precisely because it was so genuine, so guileless.• If Cynthia Coppersmith were nothing else, she was guileless.• Thorny presents sugar lumps in a plastic bowl and smiles; she expects something sinister in the smile but it is guileless.• Urquhart is a manipulative murderer who could outfox Machiavelli, while Richardson seems utterly guileless.• I was guileless and awkward in sports.• His thoughts were in turmoil and his open guileless face reflected the chaos in his mind.• She was totally guileless, honest, with a mordant sense of humour and sardonic wit. 