  Observations of the end stages of reionization indicate that at $z\approx
5-6$, the ionizing background is not uniform and the mean free path (MFP)
changes drastically. As MFP is closely related to the distribution of Lyman
Limit Systems and Damped Lyman-alpha Systems (LLSs and DLAs, or ionizing photon
"sinks"), it is important to understand them. In this study, we utilize the
CROC simulations, which have both sufficient spatial resolution to resolve
galaxy formation and LLSs alongside a fully coupled radiative transfer to
simulate the reionization processes. In our analysis, we connect the evolution
of the ionizing background and the MFP. We analyze two CROC boxes with distinct
reionization histories and find that the distribution of ionizing background in
both simulations display significant skewness that deviate from log-normal.
Further, the ionizing background in late reionization box still displays
significant fluctuations ($\sim 40\%$) at $z\approx5$. We also measure the MFP
along sightlines that start 0.15 pMpc away from the center of potential quasar
hosting halos. The evolution of the MFP measured from these sightlines exhibits
a break that coincides with when all the neutral islands disappear in the
reionization history of each box (the `ankle' of the reionization history of
the box). In the absence of LLSs, the MFP will be biased high by $\approx 20\%$
at $z\approx 5$. We also compare the MFP measured in random sightlines. We find
that at $z\approx 5$ the MFP measured in sightlines that start from massive
halos are systematically smaller by $\approx 10\%$ compared with the MFP
measured in random sightlines. We attribute this difference to the
concentration of dense structures within 1 pMpc from massive halos. Our
findings highlight the importance of high fidelity models in the interpretation
of observational measurements.
