Numerical analyses can provide greater knowledge of tsunami inundation behavior, however around structures within ports and cities traditional 2D models might not be adequate. In light of this, and considering the heavy computational burden of 3D models, this study applies a hybrid 2D-3D numerical model, that tightly couples the 2D nonlinear shallow water equations and a 3D RANS based VOF model, to the large scale simulation of the 2011 off the Pacific Coast of Tohoku Earthquake Tsunami in Kamaishi Bay. The simulation results are verified with survey data at 71 locations along the coastline and it is found the model can predict maximum inundation heights with a mean error of -7.2%. Furthermore, comparison with velocity fields obtained in a quasi-3D analysis show that the hybrid model is able to produce significant difference in flow field patterns in the 3D calculation domain.