This study provides foundational research aimed at establishing living spheres in island regions by analyzing the accessibility of basic living services in inhabited islands. By comparing accessibility levels with public service standards set primarily for inland regions, the study offers essential policy directions and data. Due to their remote nature, island regions generally exhibit poor spatial accessibility, leading to limited provision of essential services and increasing the risk of regional decline, highlighting the urgent need for tailored policy responses. Although interest in improving the welfare and living environment of island residents has grown through legislation such as the Island Development Promotion Act and the Special Act on Support for Remote Peripheral Islands, comprehensive studies on basic service conditions in these regions remain scarce. To address this gap, spatial datasets of facilities, roads, and ferry routes were constructed for 321 inhabited islands with established ferry services, and network analyses were conducted. These analyses visualized accessibility ranges and assessed service conditions across island regions. Results show that island regions, constrained by geographic isolation, often fail to meet inland-based standards for average minimum access time to basic services. This reveals a significant disparity in service accessibility between island and inland areas. The findings underscore the limitations of applying inland-centered policies uniformly to island regions and emphasize the need for differentiated standards that reflect the unique spatial characteristics of islands. Therefore, both qualitative and quantitative improvements in basic living service provision are essential for enhancing the quality of life in island communities. Overall, this study offers critical insights and baseline data for island living sphere planning and provides valuable evidence to support the development of more effective, region-specific policies for improving service accessibility in inhabited islands.