We collected the reddish foliose thalli from Koto river estuary, Yamaguchi Prefecture, on March 11, 2011. In order to identify the species, we carried out the field collections of foliose thalli from February, 2012 to March, 2013, the morphological observation in culture and PCR-RFLP analysis using the two regions of the partial mitochondrial DNA. This species at Koto river estuary was recognized visually in November, and the length of foliose thalli reached to the maximum in February. The maturation period in this species was the range from February to March. As for the morphological survey, the spherical cells were formed at the tips of conchocelis and developed to foliose thalli. The fragment patterns of this species in PCR-RFLP analysis were matched with Pyropia tenuipedalis from Jigozen, Hiroshima prefecture. In the present study, the foliose thalli collected at Koto river were identified with Py. tenuipedalis which is endangered species surrounding the coast of Japan. This species was newly recorded at Koto river estuary, Yamaguchi Prefecture.