Severe fever with thrombocytopenia syndrome (SFTS) is characterized by sudden onset of fever, leukopenia, thrombocytopenia, and gastrointestinal tract symptoms and approximately 12% of patients die from disseminated intravascular coagulation and/or multiple organ failures. Agent of the disease is a novel bunyavirus SFTS virus, and is transmitted by bite of a possible vector tick, Haemaphysalis longicornis, and through direct contact with virus-containing patient body fluids, or through unknown routes. SFTS case reports have been limited in China, and more than two thousand cases were reported in 2011 and 2012. In late 2012, a woman living in Yamaguchi prefecture in Japan showed symptoms reminiscent of those of SFTS and died 6 days after the onset of symptoms. Virus was isolated from her acute serum in Vero cells and a next generation-sequencing identified it as SFTS virus. SFTS viral genome and proteins were detected in the patient's serum. Based on the first demonstration of SFTS in Japan, a retrospective study started. Until March of 2013, totally 8 patients were diagnosed as having SFTS and the most early case was in 2005. Phylogenetic analysis of virus sequences revealed that Japanese isolates form an independent branch distinct from Chinese isolates, indicating that SFTS has been present not only in China but also in Japan.