4 in 1 is a distinctive mixed-use complex completed in 2000 and located in Ashiya, Hyogo Prefecture. Designed by architect Hiroshi Kimura of KS Architects, this innovative project masterfully combines residential and commercial functions within a single structure. The building exemplifies early 2000s Japanese architectural thinking, where urban density and diverse program integration were increasingly prioritized. Its thoughtful design approach demonstrates how residential and retail spaces can coexist harmoniously, making it a significant reference point for architects interested in multifunctional urban development and compact design solutions in residential neighborhoods.