Understanding reaction mechanisms is essential to advance the field of organic chemistry and develop novel reactions. It allows us to make sense of the clues in complex organic reactions and find a unified pattern in seemingly chaotic reactions, thereby enhancing our understanding of the reactions. In addition to developing new synthetic methodologies, our research group has conducted in-depth mechanistic investigations using various techniques, such as intermediate characterizations, spectroscopic investigations, kinetic experiments, and computational studies. By combining experimental and computational results, we have gained a comprehensive understanding of the reaction mechanism. This understanding has enabled us to rationally design reactions with novel reactivity and improved selectivity.