The Shinjuku Mitsui Building Renovation Project, completed in 2015, represents a significant urban renewal effort in Tokyo's bustling Nishi-Shinjuku district. Located at 2 Nishi-Shinjuku, Shinjuku Ward, this transportation facility underwent comprehensive modernization by the collaborative expertise of Kajima Design and Nihon Sekkei. The renovation project demonstrates contemporary architectural practices in adapting existing infrastructure to meet modern urban mobility demands. This undertaking reflects the ongoing evolution of Tokyo's transportation systems while maintaining the structural integrity and functional capacity of this important metropolitan facility. The project exemplifies sustainable urban development principles applied to major transportation hubs.