Single-molecule analysis of bio-molecules offers key benefits over macroscopic assay methods, as they unlock the ability to quantify various biological phenomena. In particular, micron/nano technologies enable highly sensitive and quantitative bioassays at the single-molecule level, which are widely used for ultra-sensitive biomedical applications, e.g., digital PCR and digital ELISA. To expand the versatility, we recently developed a novel microsystem “SATORI” with emerging CRISPR-Cas technologies that allows an accurate and rapid detection of nucleic-acid at single-molecule level. SATORI with CRISPR-Cas13a detected single-stranded RNA targets with maximal sensitivity of ∼1 aM in <9 min, thereby enabling the rapid detection of viral RNA of SARS-CoV-2. In addition, SATORI with CRISPR-Cas12a enabled single-molecule detection of double-stranded DNA, allowing the rapid detection of viral DNA of monkeypox virus. Collectively, we expect that SATORI will be one of the key technologies for future diagnostics of various infectious diseases.