open-hearted russian

• чистосерде́чный

  candid, sincere, frank, open-hearted

• простоду́шный

  open-hearted, simple-hearted, guileless, artless

  naive, simple-minded, unsophisticated

• простоду́шие

  open-heartedness, guilelessness, ingenuousness, artlessness

  simple-mindedness, naivety