As the policy paradigm is shifting toward customized welfare, customized home modification is a very important task in the area of modification. It was intended to examine a practical case in Japan that suffered serious population aging prior to Korea and is currently making efforts to address the limitations in the realization of customized welfare in this study. Such case in the advanced welfare country is an important example to obtain an insight in preventing and preparing for upcoming problems. Such case can be also referred for shifting the political paradigm and can contribute to the academic development of a new research methodology. Therefore, the purpose of this study is to analyze the process to decide improvement measures through the customized housing improvement case in Japan and the improvement effects. The method used in this study was the research of field cases, and in-depth interview and photo materials were collected and analyzed using the qualitative analysis method. The object of this study is the practical housing improvement case that a disabled male with acquired spinal paralysis carried out the desire to continue his living at his home while living with his family members. The local government and a healthcare architecture expert attempted to find the most appropriate improvement measure based on the current housing situation and the physical conditions of the residents through the collaboration. The result of this study can provide insight regarding how we can improve the environment of residential space and the interaction between residents and such result can also provide the milestone to spread the recognition on the customized housing improvement in Korea and find political directions.