Heroin is a highly addictive drug produced from morphine, which is a principal component of opium. In addition to its powerful euphoria, heroin induces both psychological and physical dependence, and thus, it is one of the most commonly used illicit drugs worldwide. In the United States, since the 1990s, the widespread use of opioids for noncancer pain has led to a vicious cycle of abuse and resale of these drugs, as well as the abuse of heroin, which can be obtained cheaply, leading to an opioid epidemic 1 and an opioid overdose crisis. 2 A recent report revealed that the prevalence of heroin use increased from 0.17% in 2002 to 0.32% in 2018 in the United States, 3 and this situation has developed into serious socioeconomic problems worldwide. In Japan, the epidemic began to spread briefly around 1960, but it has rapidly declined due to amendments to the illicit drug control law and the drug banishment campaign in Japan. In 2016, the number of heroin arrests and the number of individuals arrested were three and zero, respectively, and the amount of heroin seized was low at 4.540 g in Japan. 4 Although the indications for opioid use are increasing in Japan, its misuse or abuse has not yet become apparent. This has resulted in few opportunities to address and treat opioid use disorders in clinical psychiatric settings in Japan. However, in recent years, drug use while traveling abroad, trafficking by foreigners,