  The fraction of the contribution from yet-unresolved gamma-ray sources in the
Galactic diffuse gamma rays observed by the Tibet air shower array is an
important key to interpreting recent multi-messenger observations. This paper
shows a surprising fact: no Tibet diffuse events above 398TeV come from the
gamma-ray sources newly detected above 100 TeV by LHAASO. Based on this
observational fact, the contribution of sources unresolved by LHAASO to the
Tibet diffuse events is estimated to be less than 31% above 398TeV with a 99%
confidence level. Our result shows that unresolved sources make only a
sub-dominant contribution to the Tibet diffuse events above 398 TeV and a large
fraction of the events are truly a diffusive nature.
