This study aims to identify biomarkers (BMs) specific to α-synucleinopathies. For blood-based BMs, we will refine the serum α-synuclein (αS) seed amplification assay (SAA) by incorporating chemical and microfluidic approaches to establish a novel diagnostic technology. As an imaging BM, we will utilize the αS-PET developed by the National Institutes for Quantum Science and Technology and examine its correlation with blood BMs, as well as with pathological analyses using patient-derived iPS cells and brain tissues. Furthermore, we will explore candidate drugs that suppress αS aggregation among existing compounds. By applying both blood and imaging BMs to evaluate these candidates, we aim to establish a foundation for the development of disease-modifying therapies.