We have carried out particle physics research in order to search for New Physics beyond the Standard Model, focusing on tauonic B meson decays (B→D(*)τν) and lepton flavor violating tau-lepton decays (τ→μγ, τ→μμμetc.) at the SuperKEKB/Belle II experiment. We have completed construction of the novel particle identification detector "TOP counter", which has been developed by our own idea, and confirmed its performance. We also upgraded the computing system at Nagoya university so that we can produce large sample of simulation data efficiently and stably to prepare for the Belle II data analyses. Despite delay in the accelerator project, we could largely improved the analysis of the tauonic B-meson decays using the existing full data from the Belle experiment, and found indication of New Physics with 2.6 σ significance (3.8 σ when combined with results from other experiments in the world). The result acquired a lot of attention from particle physics community.