A wide array of extracellular vesicles within living organisms plays a crucial role in mediating physiological functions and is involved in significantly to various diseases and viral infections. Understanding the composition of these vesicles is essential to identify disease origins and develop effective diagnostics and therapeutics. However, current technologies typically analyze groups of vesicles together, leading to averaged information that lacks insight into individual vesicle components, such as the number of molecular species and their correlation with diseases. To enhance our understanding of extracellular vesicles, we have developed SATORI, a cutting-edge technology capable of identifying and rapidly detecting RNA from viruses, which are examples of extracellular vesicles, at the single-molecule level. Additionally, we created an automated platform (opn-SATORI) and a portable platform (COWFISH) based on SATORI, which serve as the initial step in clinical applications for the high-throughput diagnosis of viral infections, such as COVID-19. In this chapter, we introduce our latest technology, SATORI, and discuss its future potential for the comprehensive analysis of extracellular vesicles and use in the diagnosis of viral infections.