Tokai to Kamioka (T2K) is a long baseline oscillation experiment that measures the neutrino oscillation parameters by observing νμ (ν¯μ) disappearance and νe (ν¯e) appearance from a nearly pure νμ (ν¯μ) beam. The experiment has two near detectors 280 m from the beam production target, and one far detector located 295 km from the target. The far detector, Super-Kamiokande (SK), is a 50,000 ton water Cherenkov detector. At the energies where the T2K flux peaks (∼ 0.6 GeV), the dominant interactions are charged current quasi–elastic (CCQE), which result in single ring events. There is an ongoing effort to add multi-ring topologies such as charged current resonant pion production (CC1π+) to the T2K analysis. This addition is expected to improve the precision of sin2θ23 and Δm232 measurements. The estimation of systematic uncertainty is important for sensitivity to the neutrino oscillation parameters. One source of uncertainty is the shortcomings of the detector model, and how this impacts the event selection. The far detector systematic uncertainty is estimated via a fit to atmospheric neutrinos events observed in SK. The process of estimating the detector systematic uncertainty, including the multi-ring νμCC1π+ sample, will be presented in this poster.