Southwestern Japan, located on the eastern margin of the Eurasian continent, preserves a complex geological record shaped by oceanic subduction processes, including accretionary complexes, high- pressure metamorphism, and arc magmatism, offering crucial insights into the Late Mesozoic tectonic evolution of the East Asian continental margin. This study analyzes the tectonic evolution of Late Mesozoic Southwestern Japan, focusing on the processes of subduction- accretion complexes and volcanic- sedimentary records, and explores the links between Japan' s tectonic evolution and tectono- magmatic processes in South China. The results show that Southwestern Japan experienced sequential subduction regimes during the Late Mesozoic. The Izanagi Plate began expanding in the late Carboniferous, subducted beneath the Eurasian continent from the Early Jurassic to the Early Cretaceous, followed by the subduction of the Kula Plate during the Late Cretaceous, which terminated at the end of the Cretaceous. Based on the characteristics of Mesozoic accretionary complexes, stratigraphy, and magmatic activity, the Late Mesozoic orogeny in Southwestern Japan, induced by Paleo- Pacific Plate subduction, can be subdivided into three phases: the Early Yanshanian (~190 Ma, ~165~160 Ma), the Middle Yanshanian (~135 Ma), and the Late Yanshanian (~110~100 Ma). These phases correspond to the Yanshanian tectonic evolution observed in South China and the entire eastern part of China. These tectonic events are closely linked to the accretion of microcontinents and the process of ridge subduction. In the initial stages of Paleo- Pacific Plate (i. e. Izanagi Plate) subduction, the magmatic front rapidly advanced westward from the oceanic side to inland areas. However, from the Late Jurassic onwards, the magmatic front retreated due to the collision of microcontinents, eventually shifting to the Japan region during the Cretaceous. Cretaceous magmatism in South China was mainly controlled by asthenospheric upwelling caused by slab break- off.