1. Introduction 　In East Asian countries, rapid economic growth has driven widespread urban development. In urban areas of nations such as Singapore and China, the preservation and utilization of historic buildings are increasingly regarded as components of urban development, with policies promoting their use as tourism resources or cultural and artistic facilities (CLAIR REPORT 2020, Shimizu 2017). 　In Japan, the 2019 revision of the Act for the Protection of Cultural Properties indicated a shift toward balancing preservation with active utilization. While the conservation and use of traditional wooden structures such as temples and shrines have been extensively studied, the preservation and adaptive reuse of modern and ordinary buildings—likely to increase in the future—require new evaluative frameworks, renovation strategies, and utilization plans independent of traditional methodologies. Therefore, some researchers have begun research exploring the cultural value of modern architecture and renovation or repurposing methods for ordinary buildings (Kanai 2023, Kitagawa et al. 2013). 　The Registered Tangible Cultural Properties (hereafter referred to as “RCPs”) established under the 1996 cultural property registration system differ from the National Treasures and Important Cultural Properties in that they are not subject to strict control or rigid restoration standards. Instead, they allow for flexible renovation aimed at active use. However, unlike the National Treasures or the Important Cultural Properties, RCPs are still required to fully comply with building codes as if they were new buildings, often resulting in renovations that diminish their historical value. 　The objective of this study is to systematize the renovation methods applied in the preservation and utilization of RCPs in Japan. The significance of this research lies in contributing a practical reference for renovation techniques that aim to reconcile preservation with utilization, particularly within the context of historic buildings in East Asian countries. 2. Methodology 　This study primarily draws upon architectural journals (Shinkenchiku, Jutakutokushu) that include explanatory accounts written by renovation architects in Japan. A total of 40 case studies were analyzed which dated from the implementation of the Registered Tangible Cultural Property system in October 1996 through December 2024. We extracted the texts and drawings provided by the architects and categorized challenges associated with the reuse of existing buildings and the specific renovation techniques employed. 3. Results 　The challenges and corresponding renovation methods for the utilization of historic buildings were and classified into following six categories: (1) Structural Interventions, (2) Exterior, (3) Interior Planning and Design, (4) Barrier-Free Accessibility, (5) Fire Protection and Evacuation, and (6) Energy Efficiency and Environmental Systems. First, for structural renovations in 37 cases the challenges and methods were categorized based on major structural components: roofs, walls, columns, beams, floors, foundations, stairs, and other elements. Next, for exterior renovations in 34 cases restoration policies were categorized as either A: Prioritizing the original appearance at the time of completion, or B: Respecting the accumulated history of past renovations. Renovation approaches were further divided into; a: Renovations mimicking the original design, or b: Renovations contrasting old and new clearly distinguishing between the two. Similarly, interior planning and design methods in 37 cases were classified according to these same combinations as exterior renovations. For barrier-free design 13 cases were analyzed. These showed various approaches to providing accessible environments that enriched the architectural experience for users. For fire protection and evacuation 8 cases were examined. Some projects demonstrated how legal interpretations enabled renovations that preserved historical value. For energy efficiency and environmental systems 18 cases were studied, revealing design considerations taken during equipment upgrades. 4. Discussion 　When ensuring legal compliance, a multifaceted approach that considers the impact on the building’s exterior and interior design is essential. With the amendment to the Building Energy Efficiency Act in 2022, all buildings in Japan will be required to meet energy efficiency standards from 2025 onward, making this a major challenge going forward. When new facilities are required for utilization, there may be inconsistencies with existing layouts, necessitating alterations to the building’s original appearance. However, no cases prioritized functional improvement at the expense of the existing building’s value. Instead, renovations tended to prioritize preservation by utilizing surplus space or additions. In all renovation strategies, design decisions were made in relation to the existing architectural features. Whether through imitation of the original design or contrast between old and new, the common principle was to emphasize the original design, with no intent to overpower it through new elements. 　A limitation of this study is that the sample size is relatively small while there are 14,262 RCPs in Japan as of March 1, 2025. Future issue should focus on renovation methods for achieving compliance with the energy efficiency standards mandatory from 2025.