adjective

devoid of guile; innocent and without deception.

his face, once so open and guileless

artless,ingenuous,open,honest,sincere,genuine,naive,natural,simple,childlike,innocent,unsophisticated,unworldly,unsuspicious,trustful,trusting,honourable,truthful,frank,candid,straightforward,forthright,unaffected,unpretentious,on the up and up