Despite the strong relationship between Japan and Brazil, only few studies have been performed so far concerning the Brazilian legal system, especially in the sphere of criminal procedure. The purpose of this study is to survey the criminal investigation system, i.e., the first step in criminal procedure, in Brazil. There are a variety of criminal investigation systems in Brazil; this study focuses on the investigations conducted by judicial police, which comprise the overwhelming majority of investigations for criminal cases. First, the nature of Brazilian criminal investigations is examined. Two main principles are adopted in this context worldwide: i.e., adversarial or inquisitorial principles. Which system is adopted in Brazil? In the current situation, where the adopted principle is compromised in most countries, what is the Brazilian experience? Second, the system must review the processes of criminal investigation in Brazil. The procedure to start, the time to take, and how to close the investigation are focused on in this study, which concludes with a summary from a comparative law perspective.