Neutrino oscillation studies enters the precision measurement era.  CP asymmetry in  electron neutrino and anti-neutrino appearances can be as large as 20% depending on the CP phase δcp, which is within reach of new projects aiming at statistical errors of ~3% such as HyperK and DUNE. In order to successfully observe CP asymmetry, controlling  the systematic uncertainty down to 2-3% (or less!) is required. The current  PDG summary of the atmospheric neutrino mixing is consistent with maximal  (sin^2(θ23)=0.51±0.04), possibly indicating μ-τ symmetry in lepton mixing is it persists. On the other hand, the 68% interval of sin^2(θ23) that this is supposed to be based are 0.382-0.434 for NOvA experiment and 0.464-0.538 for T2K, exhibiting slight tension. Systematic uncertainty is the major issue for both experiments,  in particular from nuclear/hadronic effects such as the final state interaction.  Systematic uncertainties, such as theoretical model dependence, do not necessarily  follow a Gaussian distribution, and it is not trivial to properly  estimate 3σ or 5σ sensitivity when the contributions from the systematic uncertainties  becomes significant in the measurements. In this seminar, I will describe essential challenges and opportunities in handling systematic uncertainties in precision neutrino physics measurements, and describe emerging efforts to handle them.