Leeches (members of the subclass Hirudinida) are well known as "boold-suckers". On the other hand, this taxon also contains many predaceous leeches. I specialize in Systematic Hirudinology focusing especially on such non-blood sucking taxa. During my study, I have described 17 Orobdella species from Japan, Taiwan, and Russian Far East. In addition to these new species descriptions, I have clarified the taxonomic status of the known leeches, e.g., Orobdella whitmani Oka, 1895 and Mimobdella japonica Blanchard, 1897, which were described more than 100 years ago. These leech studies have been carried out with many research collaborators.

I have conducted leech surveys not only in Japan, but also in the other countries: Malaysia, South Korea, Taiwan, Thailand, Russia and Vietnam. There are still many undescribed leech species in Asia. Those leeches should be described as a new species, and their phylogenetic positions should be estimated by appropriate methods in the future. Only systematic studies can reveal the true species diversity and evolutionary history of leeches.