Masato Shimon (子門 真人, Shimon Masato?, January 4, 1944–) is a retired Japanese vocalist from Meguro, Tokyo. He is most known for his contributions to the theme songs of various anime and tokusatsu series. In his career, he has sung under the names Koichi Fuji (藤 浩一, Fuji Kōichi?) and Akira Tani (谷 あきら, Tani Akira?). "Masato Shimon" is also his recording name, as he was born with the name Masaharu Fujikawa (藤川 正治, Fujikawa Masaharu?). He recorded a song "Oyoge! Taiyaki-kun" (1975) with only 50,000 yen, but the single sold 4,547,620 copies and became the best-selling single in Japan, a fact certified by Guinness World Records.