The stalked sea squirt, Styela clava, was examined for the presence of the kinetoplastid, Azumiobodo hoyamushi, the causative agent of soft tunic syndrome in the edible ascidian, Halocynthia roretzi. Apparently healthy S. clava individuals were collected from a H. roretzi culture site, which was epizootic area of A. hoyamushi. After rearing for 50 days, the tunics of seven out of 48 specimens became softened and were found infected with A. hoyamushi. Healthy H. roretzi were experimentally infected with A. hoyamushi by rearing in water containing tunic from the diseased S. clava. Our results indicate that S. clava is a potential carrier of A. hoyamushi.