Literally: empty – empty – truth – truth
Alternately: Two sides in a fierce battle, using every strategy and wile they can think of. Striving to avoid your enemy’s strengths (実) and attack their weaknesses (虚). Alternately, using a mixture of truth and falsehood in an attempt to draw out someone’s true feelings.
Notes: The second of each doubled character may be replaced with the doubling mark 々… but please use it for either neither of them, or both; don’t use it with just one kanji and leave the other.