Question: Hiroaki Sato fought which Japanese mixed martial artist born on July 21, 1981?
Sentence (from "Hikaru Sato"): During the next eight years, Sato fought, on average, five times a year, compiling a record of 18 wins, 19 losses and four draws, which included fights against the likes of Keiichiro Yamamiya, Nathan Marquardt, Ryo Chonan and Yushin Okami.
Relevant evidence: Yes