Sincere. a : free of dissimulation : honest <a sincere interest>
b : free from adulteration : pure <a sincere doctrine> <sincere wine>
2 : marked by genuineness : true
— sin·cere·ly adverb
— sin·cere·ness noun
Note# Many people who suffer from OCD, Autism, Aspergers, Schizoaffective and/or Schizophrenia can be nothing but sincere. Their sincerity makes it difficult for them to live in society.